Avoiding a Long War

U.S. Policy and the Trajectory of the Russia-Ukraine Conflict

by Samuel Charap, Miranda Priebe

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Ukrainian servicemen are seen near the frontline in Soledar, Donetsk region, Ukraine, January 23, 2023, photo by Oleksandr Ratushniak/Reuters

Ukrainian servicemen are seen near the frontline, amid Russia's attack on Ukraine, near Soledar in Donetsk region.

Photo by Oleksandr Ratushniak/Reuters

How does this end? Increasingly, this question is dominating discussion of the Russia-Ukraine war in Washington and other Western capitals. Although successful Ukrainian counteroffensives in Kharkiv and Kherson in fall 2022 renewed optimism about Kyiv's prospects on the battlefield, Russian President Vladimir Putin's announcement on September 21 of a partial mobilization and annexation of four Ukrainian provinces was a stark reminder that this war is nowhere near a resolution. Fighting still rages across nearly 1,000 km of front lines. Negotiations on ending the conflict have been suspended since May.

The trajectory and ultimate outcome of the war will, of course, be determined largely by the policies of Ukraine and Russia. But Kyiv and Moscow are not the only capitals with a stake in what happens. This war is the most significant interstate conflict in decades, and its evolution will have major consequences for the United States. It is appropriate to assess how this conflict may evolve, what alternative trajectories might mean for U.S. interests, and what Washington can do to promote a trajectory that best serves U.S. interests.

Some analysts make the case that the war is heading toward an outcome that would benefit the United States and Ukraine. Ukraine had battlefield momentum as of December 2022 and could conceivably fight until it succeeds in pushing the Russian military out of the country. Proponents of this view argue that the risks of Russian nuclear use or a war with the North Atlantic Treaty Organization (NATO) will remain manageable.[1] Once it is forced out of Ukraine, a chastened Russia would have little choice but to leave its neighbor in peace—and even pay reparations for the damage it caused. However, studies of past conflicts and a close look at the course of this one suggest that this optimistic scenario is improbable.

In this Perspective, therefore, we explore possible trajectories that the Russia-Ukraine war could take and how they might affect U.S. interests. We also consider what the United States could do to influence the course of the conflict.

An important caveat: This Perspective focuses on U.S. interests, which often align with but are not synonymous with Ukrainian interests. We acknowledge that Ukrainians have been the ones fighting and dying to protect their country against an unprovoked, illegal, and morally repugnant Russian invasion. Their cities have been flattened; their economy has been decimated; they have been the victims of the Russian army's war crimes. However, the U.S. government nevertheless has an obligation to its citizens to determine how different war trajectories would affect U.S. interests and explore options for influencing the course of the war to promote those interests.

Key Dimensions That Define Alternative War Trajectories

Numerous analysts have posited scenarios for the war's short-term trajectory—or even for endgames.[2] Although such scenarios are important constructs for thinking about the future, they are less helpful for determining what possible developments matter most to the United States. It is perhaps more useful for U.S. policymakers to consider which particular aspects of the conflict's future development will have the most significant impact on U.S. interests. In lieu of rich, descriptive scenarios, we examine five key dimensions that define alternative war trajectories:

- possible Russian use of nuclear weapons

- possible escalation to a Russia- conflict

- territorial control

- duration

- form of war termination.

In this section, we describe each of these dimensions, consider how they could vary as the war progresses, and explore the relationships among them. We also explain how different variations of these five dimensions would affect U.S. interests.

Possible Russian Use of Nuclear Weapons

The specter of Russian nuclear use has haunted this conflict since its early days. In announcing his invasion in February 2022, Putin threatened any country that tried to interfere in Ukraine with consequences "such as you have never seen in your entire history."[3] He went on to order a "special regime of combat duty" for Russia's nuclear forces a week later.[4] In October 2022, Moscow alleged that Kyiv was planning to detonate a radioactive "dirty bomb" in Ukraine as a false flag operation and then blame Russia. U.S. officials worried that Russia was promoting this story to create a pretext for using nuclear weapons.[5] And perhaps most disconcertingly, Western governments appear to have become convinced that Moscow considered using nonstrategic nuclear weapons (NSNW) as its forces lost ground in the fall. Russia has denied these allegations, but news reports suggest that top Russian commanders did discuss this option.[6]

Some analysts have dismissed the possibility of  use, contending that Russia knows that employment of nuclear weapons would be self-defeating. They point to the lack of high-value military targets (for example, concentrated Ukrainian forces) that could be effectively destroyed with such weapons and to the risk that these weapons might harm Russian troops deployed in Ukraine. Use of these weapons could provoke  entry into the war, erode Russia's remaining international support, and spark domestic political backlash for the Kremlin. Knowing this, the logic goes, Russia would be deterred from using nuclear weapons.[7]

These arguments ignore several issues that make Russian use of nuclear weapons both a plausible contingency that Washington needs to account for and a hugely important factor in determining the future trajectory of the conflict. First, there is evidence that the Kremlin perceives this war to be near existential. Ukraine has long been in a category of its own in Russian foreign policy priorities; even before the 2022 war, Russia was willing to devote significant resources and make major trade-offs to pursue its objectives in Ukraine.[8] For example, Moscow paid dearly for its 2014 annexation of Crimea and invasion of eastern Ukraine. Western sanctions cost an average of 2 percent in quarter-on-quarter decline in Russia's gross domestic product between mid-2014 and mid-2015, an effect that compounded as the sanctions continued in subsequent years.[9] Putin's decision to launch a full-scale invasion in February 2022, despite clear warnings from the United States and its allies that he would pay a much higher price than in 2014, shows that he is willing to go to even more-extreme lengths to pursue his objectives in Ukraine. The decision to mobilize 300,000 Russians in September 2022 arguably upended a domestic social order that Putin spent nearly 25 years building, which also signals a high level of resolve.[10] That order was premised on avoiding the kinds of social instability that mobilization introduced, particularly for Putin's core supporters. The decision to mobilize was postponed until it was past due from a military perspective to avoid these domestic political costs—and the perceived risks of potential unrest stemming from an ebbing of popular support for the regime. Putin's willingness to accept these domestic costs and risks underscores the importance he attaches to Russian interests in Ukraine.

Second, since Russia's conventional capabilities have been decimated in Ukraine, Moscow's nonnuclear escalatory options are limited. If Russia experiences further large-scale battlefield losses, desperation could set in among senior Kremlin decisionmakers. Once other conventional escalatory options have been exhausted, Moscow may resort to nuclear weapons, and specifically  use, to prevent a catastrophic defeat.

Third, Russian strategists have long highlighted the utility of  for accomplishing operational and tactical goals in the context of a conventional war that Moscow is losing. And Russia has capabilities to carry out these concepts: Its  delivery systems include artillery, short-range ballistic missiles, and cruise missiles, all of which could be employed in Ukraine.[11] Russian strategists also envision preemptive employment of  against civilian targets—cities, military-industrial centers, and government facilities—and against military ones, at least in the context of a war with .[12] Moscow also could use  for demonstration strikes, either in the atmosphere or targeted at population centers.[13] The military effectiveness of  employment in Ukraine might be subject to debate, but it is a plausible contingency given what is known about Russian planning and capabilities.

Although Russian nuclear use in this war is plausible, we cannot determine precisely how likely such use is. What we can say is that the risk of nuclear use is much greater than in peacetime. We can also say that nuclear use would be highly consequential for the United States.

The United States has signaled both publicly and, reportedly, in direct contact with the Kremlin that it would retaliate if Russia were to employ nuclear weapons in Ukraine.[14] U.S. officials have avoided specifying the exact nature of a possible response—instead using such phrases as "catastrophic consequences"—but one  official said it would "almost certainly" entail a "physical response from many allies."[15] Although this formulation does not explicitly commit to a military response, even a nonmilitary retaliation that entails "catastrophic consequences" for Russia might lead to a tit-for-tat spiral that produces a -Russia war. Russian  use in Ukraine could therefore lead to a direct U.S. conflict with Russia, which could ultimately result in a strategic nuclear exchange.[16]

But even if the escalatory challenges could be managed, Russian nuclear use in Ukraine would be highly consequential for the United States. If Russia won concessions or made military gains through nuclear use, the norm against nonuse would be weakened and other countries might be more likely to use such weapons in future conflicts. Moreover, Russian use of nuclear weapons in Ukraine would have large and unpredictable effects on allied policies toward the war, potentially leading to a breakdown in transatlantic unity. Death and destruction in Ukraine, a tragedy in itself, could also have a major impact on U.S. and allied publics. In short, the Biden administration has ample reason to make the prevention of Russian use of nuclear weapons a paramount priority for the United States.

Possible Escalation to a Russia- Conflict

Although a Russian decision to attack a  member state is by no means inevitable, the risk is elevated while the conflict in Ukraine is ongoing.

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Since October 2021, when he first briefed President Joe Biden on Russia's plans to invade Ukraine, Chairman of the Joint Chiefs of Staff Mark Milley reportedly kept a list of "U.S. interests and strategic objectives" in the crisis: "No. 1" was "Don't have a kinetic conflict between the U.S. military and  with Russia." The second, closely related, was "contain war inside the geographical boundaries of Ukraine."[17] To date, Russia and Ukraine remain the only combatants in the war. But the war could still draw in U.S. allies. Combat is taking place in a country that borders four  member states on land and shares the Black Sea littoral with two others. The extent of  allies' indirect involvement in the war is breathtaking in scope. Support includes tens of billions of dollars' worth of weapons and other aid given to Ukraine, tactical intelligence, surveillance and reconnaissance support to the Ukrainian military, billions of dollars monthly in direct budgetary support to Kyiv, and painful economic sanctions imposed on Russia.

A previous RAND Corporation report outlined four plausible pathways to an intentional Russian decision to strike  member states in the context of the war in Ukraine. It identified the following reasons:[18]

- Punish  members for policies already underway with the objective of ending allied support for Ukraine.

- Strike  preemptively if Russia perceives that  intervention in Ukraine is imminent.

- Interdict the transfer of arms to Ukraine that Russia believes might cause its defeat.

- Retaliate against  for perceived support for internal unrest in Russia.

Although a Russian decision to attack a  member state is by no means inevitable, in part because it could lead to a war with a far more powerful alliance, the risk is elevated while the conflict in Ukraine is ongoing. Moreover, inadvertent escalation that leads to  entry into the conflict is also an ongoing risk. Although the November 2022 incident involving a Ukrainian air defense missile landing on Polish territory did not spiral out of control, it did demonstrate that fighting can unintentionally spill over to the territory of neighboring U.S. allies. A future targeting error could send a Russian missile into  territory, potentially sparking an action-reaction cycle that could lead to a full-scale conflict. If the war in Ukraine were to end, the likelihood of a direct Russia- clash, whether intentional or inadvertent, would diminish significantly.

It is clear why Milley listed avoiding a Russia- war as the top U.S. priority: The U.S. military would immediately be involved in a hot war with a country that has the world's largest nuclear arsenal. Keeping a Russia- war below the nuclear threshold would be extremely difficult, particularly given the weakened state of Russia's conventional military. Some analysts are doubtful that Russia would attack a  country since it is already losing ground to Ukrainian forces and would find itself in a war with the world's most powerful alliance.[19] However, if the Kremlin concluded that the country's national security was severely imperiled, it might well deliberately escalate for lack of better alternatives.

Territorial Control

As of December 2022, Russia occupied nearly 20 percent of Ukraine. Kyiv's top priority is regaining control over this territory. And Ukraine has scored some impressive successes, particularly in Kharkiv and Kherson. Yet the areas Russia still controls contain important economic assets, such as the Zaporizhzhia Nuclear Power Plant, which provided up to 20 percent of Ukraine's prewar power generation capacity, and Ukraine's entire Azov Sea coastline. President Volodymyr Zelenskyy is committed to a military campaign to liberate the entirety of Ukraine's internationally recognized territory. And he has justified this objective with the moral imperative of liberating his country's citizens from brutal Russian occupation.

A war trajectory that allows Ukraine to control more of its internationally recognized territory would be beneficial for the United States (Table 1). The United States has an interest in showing that aggression does not pay and reinforcing the territorial integrity norm that is enshrined in international law.[20] However, the implications for that interest of further Ukrainian territorial control beyond the December 2022 line are not clear-cut. For example, even if Ukraine took control over all of the territory that Russia had seized since February 24, 2022, Moscow would still be in violation of the territorial integrity norm. Put differently, it is not clear that a trajectory that entails Russia maintaining the December 2022 line of control would do more harm to the international order than one that saw Russian forces pushed back to the February line. In both cases, Russia would control some Ukrainian territory in violation of the territorial integrity norm.

Table 1. Potential Benefits of Greater Ukrainian Territorial Control for the United States

Benefit

Explanation

Highly significant benefits

blank

blank

Moderately significant benefits

Fewer Ukrainians would be living under Russian occupation.

The United States has a humanitarian interest in exposing fewer Ukrainians to Russian occupation.

Less significant benefits

Ukraine could become more economically viable and less dependent on external assistance.

Areas under Russian control as of December 2022 are unlikely to prove hugely economically significant.

Ukrainian control of more of its sovereign land may reinforce the territorial integrity norm.

Barring full Ukrainian territorial reconquest, Russia will remain in violation of the norm.

NOTE: Our weighting, detailed in the text, combines an assessment of consequences of an outcome to the United States and the likelihood of an outcome occurring.

An end to the war that leaves Ukraine in full control over all of its internationally recognized territory would restore the territorial integrity norm, but that remains a highly unlikely outcome.

Furthermore, the weakening of the norm is less a function of the quantity of land illegally seized than it is a consequence of the international community's acceptance of the territorial change. The United States need not (and almost certainly would not) formally recognize any Russian occupation of sovereign Ukrainian territory regardless of where the de facto line of control is drawn. As it did with Crimea, the United States can take measures to ensure any Russian gains since February 24, 2022, are treated as illegitimate and illegal and that Russia pays a steep price for its aggression.

The extent of Kyiv's control over its territory could affect the long-term economic viability of the country and thus its needs for U.S. assistance. For example, if Moscow took over Ukraine's entire Black Sea coast, leaving Ukraine landlocked, that would pose severe long-term economic challenges for the country. However, this outcome seems unlikely given Russia's military performance to date. The economic impact of Russia's possible long-term control over areas it occupied in December 2022 compared with what it held on February 23, 2022—although difficult to calculate precisely—would be far less severe. The economic effects of any lost territory will depend on the productivity of those areas and the extent of their interconnectedness with the rest of Ukraine. Regardless, Ukraine's economy would eventually adjust to any line; the question is how painful that adjustment would be. Additionally, given Russia's ability to strike deep beyond the current line of control (or any line of control), greater territorial control is not directly correlated with greater economic prosperity—or, for that matter, greater security. As Kyiv has retaken more territory since September, Russia has imposed far greater economic costs on the country as a whole through its strikes on critical infrastructure. An ongoing threat of Russian attacks could inhibit investment and therefore economic recovery throughout Ukraine regardless of how much territory Moscow controls.

In sum, greater Ukrainian territorial control is important to the United States for humanitarian reasons, to reinforce international norms, and to foster Ukraine's future economic growth. However, the significance of the two latter benefits are debatable. Russia's violations of international norms long predate the current conflict and are likely to persist after the fighting ends. Moreover, the United States and its allies have imposed many other types of costs on Russia for its aggression—costs that have already sent a signal to other would-be aggressors. And the line of control as of December 2022 does not deprive Kyiv of economically vital areas that would dramatically affect the country's viability.

In addition to these benefits, greater Ukrainian territorial control also poses potential costs and risks for the United States (Table 2). First, given the slowing pace of Ukraine's counteroffensives in December 2022, restoring the pre-February 2022 line of control—let alone the pre-2014 territorial status quo—will take months and perhaps years to achieve. Russia has built substantial defensive fortifications along the line of control, and its military mobilization has rectified the manpower deficit that enabled Ukraine's success in the Kharkiv counteroffensive. A long war is likely to be necessary to allow Kyiv the time it would need to restore control over significantly more land. As we describe in the following section, a long war could entail major costs for the United States. Furthermore, if Ukraine does push beyond the pre-February 2022 line of control and manages to retake areas that Russia has occupied since 2014 (particularly Crimea, where the Russian Black Sea Fleet is based), the risks of escalation—either nuclear use or an attack on —will spike. The Kremlin would likely treat the potential loss of Crimea as a much more significant threat both to national security and regime stability, given the assets deployed there and the political capital invested in the annexation of the peninsula.

Table 2. Potential Costs of Greater Ukrainian Territorial Control for the United States

Cost

Explanation

Highly significant costs

Enabling greater Ukrainian territorial control increases the risk of a long war.

A long war poses significant challenges for U.S. interests (see Table 4).

There is a higher risk of Russian nuclear weapons use or a -Russia war if Ukraine pushes past the February 24, 2022, line of control.

Avoiding these two forms of escalation is the paramount U.S. priority.

Moderately significant costs

blank

blank

Less significant costs

blank

blank

NOTE: Our weighting, detailed in the text, combines an assessment of consequences of an outcome to the United States and the likelihood of an outcome occurring.

Duration

We do not know how long this war will last. Some have suggested it could end in negotiations over the winter of 2022–2023.[21] Others have argued it will go on for years.[22] Many in the United States are reluctant to push for an end to the conflict at a time when Ukraine has momentum on the battlefield and the Ukrainian people seem willing to endure the costs of a long war to achieve their goals.

Although a longer war might enable the Ukrainian military to retake more territory, there are other implications of the war's duration for U.S. interests. A protracted conflict, as perverse as it might seem, has some potential upsides for the United States (Table 3). While the war continues, Russian forces will remain preoccupied with Ukraine and thus not have the bandwidth to menace others. A longer war would further degrade the Russian military and weaken the Russian economy. But the war has already been so devastating to Russian power that further incremental weakening is arguably no longer as significant a benefit for U.S. interests as in the earlier phases of the conflict. It will take years, perhaps even decades, for the Russian military and economy to recover from the damage already incurred.

Table 3. Potential Benefits of a Long War for the United States

Benefit

Explanation

Highly significant benefits

blank

blank

Moderately significant benefits

Russia will be further weakened.

Russia has already been significantly weakened by the war, so the United States would only see moderate benefits from further weakening its adversary.

Less significant benefits

Greater Ukrainian territorial control is possible.

Benefits of greater Ukrainian territorial control are moderately or less significant (see Table 1).

Russia's ability to menace others is limited while the war is ongoing.

As long as the fighting continues, the Russian military and its leaders will have much less bandwidth to intervene elsewhere.

Allies may further reduce energy dependence on Russia and increase spending on their own defense.

The trends appear to be well established already.

NOTE: Our weighting, detailed in the text, combines an assessment of consequences of an outcome to the United States and the likelihood of an outcome occurring.

A long war would also maintain pressure on European governments to continue to reduce energy dependence on Russia and spend more on their defense, possibly lessening the U.S. defense burden in Europe over the long run. Here too, however, it is likely that European countries will maintain these policies regardless of how much longer the war lasts.

Yet there are significant downsides of a long war for U.S. interests (Table 4). A longer war will lead to further loss of life, displacement, and suffering for Ukrainian civilians; minimizing these humanitarian consequences for Ukraine is a U.S. interest. Continued conflict also leaves open the possibility that Russia will reverse Ukrainian battlefield gains made in fall 2022. Moscow's mobilization might stabilize the lines as of December 2022 and allow Russia to launch offensives in 2023. The intensity of the military assistance effort could also become unsustainable after a certain period. Already, European and some U.S. stocks of weapons are reportedly running low.[23] There is thus reason to question whether a longer war will lead to further Ukrainian gains—losses are possible too.

Table 4. Potential Costs of a Long War for the United States

Cost

Explanation

Highly significant costs

There would be a prolonged elevated risk of Russian nuclear use and a -Russia war.

Avoiding these two forms of escalation is the paramount U.S. priority.

Moderately significant costs

Ukraine would have a greater need for external economic and military support during and after the war.

Returning Ukraine to economic sustainability would alleviate strain on U.S. and allied budgets and stockpiles.

More Ukrainian civilians would die, be displaced, or endure hardships stemming from the war.

The United States has a humanitarian interest in reducing the suffering of the Ukrainian people.

There would be continued upward pressure on energy and food prices, causing loss of life and suffering globally.

The United States has an interest in stable energy markets and minimizing global food insecurity and associated human suffering.

Global economic growth would slow.

Global economic trends affect the U.S. economy.

The United States would be less able to focus on other global priorities.

U.S. resources, forces, and senior-leader attention are not being devoted to other U.S. priorities.

An ongoing freeze in U.S.-Russia relations would pose challenges to other U.S. priorities.

Bilateral or multilateral interaction with Russia on key U.S. interests will be highly contentious while the war is ongoing.

Less significant costs

There is a possibility of Russian territorial gains.

Russia is not likely to make significant territorial gains.

Russian dependence on China could increase.

Russia will be more dependent on China than it was before the war regardless of its duration.

NOTE: Our weighting, detailed in the text, combines an assessment of consequences of an outcome to the United States and the likelihood of an outcome occurring.

The costs for the United States and the European Union of keeping the Ukrainian state economically solvent will multiply over time as conflict inhibits investment and production; Ukrainian refugees remain unable to return; and, as a result, tax revenue and economic activity drop dramatically lower than before the war. Russia's campaign of destruction of Ukrainian critical infrastructure will create major long-term challenges for sustaining the war effort and for economic recovery and has also substantially increased Kyiv's projections for the economic support it will need from the United States and its allies.[24]

Global economic disruptions stemming from the war will continue and possibly multiply as long as the conflict goes on. The outbreak of war caused a sharp increase in energy prices that has in turn contributed to inflation and slowing economic growth globally. These trends are expected to hit Europe hardest.[25] The increase in energy prices alone is likely to lead to nearly 150,000 excess deaths (4.8 percent more than average) in Europe in the winter of 2022–2023.[26] The war has also contributed to rising food insecurity globally. Ukraine's exports of grains and oilseeds dropped to 50 to 70 percent of their prewar levels between March and November 2022, partly because of Russia's naval blockade and attacks on energy infrastructure. Russia has also restricted its own exports of fertilizer, of which it is the largest global producer. The result has been a large increase in food and fertilizer prices globally. Although food prices came down somewhat after Russia agreed to allow Ukrainian grain exports out of certain Black Sea ports in July 2022, prices as of December 2022 remained above their prewar levels. These effects of the war came at a time when food insecurity was already rising as a result of extreme weather, the coronavirus disease 2019 (COVID-19) pandemic, and other global trends.[27]

Beyond the potential for Russian gains and the economic consequences for Ukraine, Europe, and the world, a long war would also have consequences for U.S. foreign policy. The U.S. ability to focus on its other global priorities—particularly, competition with China—will remain constrained as long as the war is absorbing senior policymakers' time and U.S. military resources. Bilateral or multilateral interaction—let alone cooperation—with Russia on key U.S. interests is unlikely. For example, the prospects for negotiating a follow-on to the New START strategic arms control treaty, which expires in February 2026, will remain dim as long as the war continues. Globally, persistent sky-high tensions with Russia would continue to cripple the work of multilateral institutions, such as the United Nations (UN) Security Council, and limit the capacity for collective responses to shared challenges. Russia's deepening military cooperation with Iran during this war—at a time when Iran is reneging on its commitments to restrain its nuclear program—suggests that Moscow could play the spoiler on such issues as nonproliferation. And although Russia will be more dependent on China regardless of when the war ends, Washington does have a long-term interest in ensuring that Moscow does not become completely subordinated to Beijing. A longer war that increases Russia's dependence could provide China advantages in its competition with the United States.

Finally, the duration of the war is directly related to the two escalation contingencies discussed earlier (possible Russian use of nuclear weapons and possible escalation to a Russia- conflict). For as long as the war continues, the risk of both forms of escalation will remain heightened. The risk will be dramatically lower when the war ends. Therefore, the paramount U.S. interest in minimizing escalation risks should increase the U.S. interest in avoiding a long war.[28]

In short, the consequences of a long war—ranging from persistent elevated escalation risks to economic damage—far outweigh the possible benefits.

Form of War Termination

The literature on war termination suggests three possible ways that the Russia-Ukraine war could end: absolute victory, armistice, and political settlement. For the purposes of this analysis, we do not consider operational pauses, temporary cease-fires, and agreements that break down. Our focus is on the form in which the war eventually ends, not the ebbs and flows along the way to such an outcome.

Absolute Victory

Since neither side appears to have the intention or capabilities to achieve absolute victory, the war will most likely end with some sort of negotiated outcome.

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One form of war termination is an absolute victory. This outcome involves one state "permanently removing the (interstate) threat posed by its adversary." Absolute victory, as Dan Reiter notes, can be accomplished through "the victor installing a new leadership in the defeated state, occupying or annexing the adversary's territory, or at worst annihilating the adversary's entire population." Although it might entail an agreement, an absolute victory's defining feature is "a war outcome that essentially removes the possibility of the defeated state reneging on a war-ending settlement."[29] This is the type of victory that the allies achieved over Japan and Germany at the end of World War II.

When the war began, Moscow appeared to be seeking an absolute victory, with plans to install a new regime in Kyiv and "demilitarize" the country. Since abandoning its attempt to take the capital in early April, Russia appears to have scuttled these plans. Putin's declared aims have varied over time since then, but at no point in recent months have he or his ministers repeated the direct calls to overthrow the government in Kyiv issued in the early weeks of the war. Although some allege that Moscow has not given up on its initial ambitious goals, even if the Kremlin still aspired to impose an absolute victory, facts on the ground indicate that it would not be able to do so. As of this writing, Moscow's primary goal seems to be holding onto territory in the four Ukrainian regions that Russia now claims as its own. But even if Russia took and held those regions, that would hardly be an absolute victory; it would have to effect a fundamental change in Ukraine's political system, such as ousting President Zelenskyy, to achieve absolute victory. But Ukraine's system of government is now more firmly anchored than it was before the war, Russia's brutal tactics have repelled even those Ukrainians who harbored pro-Russian sympathies, and Zelenskyy is immensely popular. Moreover, the Ukrainian military, with its current capabilities, could pose a threat to Russian occupied areas or even the bordering areas of undisputed Russian territory indefinitely.

An absolute Ukrainian victory is also unlikely. Ukraine has never officially proclaimed an intention to achieve an absolute victory as the literature defines it. President Zelenskyy's declared objectives have changed over time, but, as of December 2022, his stated goal is to retake all of Ukraine's territory, including Crimea and the areas of the Donbas that Russia has occupied since 2014. Still, complete territorial reconquest would not constitute an absolute victory. If the Ukrainian military were to eject Russian forces from Ukraine, they would doubtless seriously degrade the Russian army in the process. Nonetheless, Russia would have a wide variety of capabilities on its territory and beyond—particularly the navy and the aerospace forces, which have not taken major losses in the war—that could enable continued strikes on targets deep within Ukraine. Russian ground forces could readily regroup and launch another large-scale offensive. To achieve absolute victory, Ukraine would have to deny Russia the ability to contest its territorial control. Forcing the Russian military to cross the international border would not produce that outcome. And although Ukraine has surprised observers with its ability to defend its own homeland, it is fanciful to imagine that it could destroy Russia's ability to wage war.

Therefore, Kyiv would probably need regime change in Moscow in addition to victory on the battlefield to avoid living under the constant threat of reinvasion.[30] Some analysts contend that Russia's poor performance in the war, mounting casualties, and mobilization could cause political instability and lead to Putin's overthrow and replacement with a new regime that would stop fighting, come to terms with Ukraine, and pose a diminished threat over the long term.[31] However, there is little historical evidence to suggest that regime change in Russia would necessarily ensue following battlefield failures. Leaders of personalist regimes like Russia's have often remained in power after a military defeat.[32] Moreover, there is no guarantee that a new Russian leader would be any more inclined to make peace with Ukraine than Putin is. As Shawn Cochran writes, "it is difficult and probably pointless to predict the outcome of any wartime change of leadership in the case of Russia's war in Ukraine. At a minimum, however, the West should not assume a change of leadership would result in an end to the war, at least in the short term, as Putin's war could very well continue without Putin."[33] Moreover, regime change in Moscow might not reduce the intensity of the competition between the United States and Russia on other issues. Regardless, Kyiv has not proclaimed regime change as its stated objective, although some Ukrainians understandably hope for it.

Since neither side appears to have the intention or capabilities to achieve absolute victory, the war will most likely end with some sort of negotiated outcome. Negotiated ends to wars, unlike absolute victories, require the belligerents to accept a degree of risk that the terms of the peace could be violated; even the relative "loser" in the conflict will retain the ability to threaten the other side. Agreements to end wars are highly contingent on the particulars of a given conflict, but it is analytically useful to distinguish between lasting cease-fires or armistice agreements on the one hand and political settlements on the other.

Armistice Agreements

In armistice agreements, like those that ended the Korean War in 1953 and the Transnistria conflict in Moldova in 1992, the two sides commit to stop fighting and often create mechanisms, such as demilitarized zones, to prevent the resumption of violence.[34] Although armistice agreements can be quite detailed (the Korea agreement was nearly 40 pages long), they generally do not address the political drivers of the conflict, which means tensions can endure and diplomatic and economic relations between the parties often remain at a minimal level. Armistice agreements that have mechanisms for monitoring and ensuring compliance to reduce the risk of conflict resuming are more durable than those that do not.[35]

An armistice in Ukraine would freeze the front lines and bring a long-term end to active combat. Russia would stop attempts to occupy additional Ukrainian territory and cease missile strikes on Ukrainian cities and infrastructure. Ukrainian forces would stop their counteroffensives—strikes on Russian-held areas of Ukraine and on Russia itself. There would still be ongoing, unresolved territorial disputes (that is, divergent positions on the location of Ukraine's borders) between Kyiv and Moscow; these would be contested politically and economically, not militarily. The key political issues beyond territorial control, ranging from Russian payment of reparations to Ukraine's geopolitical status, would remain unaddressed. The sides would likely conduct only minimal trade; the borders would be largely closed. The line of control would likely become highly militarized, like the inner German border during the Cold War.

Political Settlement

A political settlement or peace treaty would involve both a durable cease-fire and a resolution of at least some of the disputes that sparked the war or emerged during it. Since 1946, peace treaties have been less common than armistice agreements, but they tend to produce a durable end to fighting and reduction in tensions.[36] In the case of the Russia-Ukraine war, a settlement would entail negotiated compromises on some of the core political issues at stake for the two sides. The Russia-Ukraine bilateral negotiations in the early weeks of the war, which culminated in the Istanbul Communique released at the end of March, and more-recent statements from political leaders give hints about some issues a political settlement could cover.[37] For Russia, codifying Ukraine's nonalignment would likely be central. Ukraine would want reinforced Western commitments to its security since it does not trust Russia to comply with any agreement. A settlement could cover a host of other issues, such as a reconstruction fund, bilateral trade, cultural matters and freedom of movement, and conditions for relief of Western sanctions on Russia.

A political settlement need not cover all this ground or it could address other issues. But the core outcome would be a return to some degree of normal relations between the former belligerents. Importantly, the parties could agree to disagree about the status of certain territory even while reaching terms on other issues. For example, the Soviet Union and Japan normalized diplomatic and trade relations in 1956, but the territorial disputes between Moscow and Tokyo were never resolved. A political settlement does not have to definitively resolve all the differences between the parties; it does need to address enough of these differences to qualitatively improve the broader relationship between the former belligerents.

These two categories of negotiated ends to wars—armistices and political settlements—are often not so clearly differentiated in practice: many cease-fire agreements address some political issues, and some settlements, as noted, leave key political disputes unresolved. A negotiated end to the war in Ukraine is likely to fall somewhere between these two ideal types.

Implications for U.S. Interests

Since an absolute victory is highly unlikely, there will probably be a negotiated end to the Russia-Ukraine war at some point.[38] But, given current trends, the prospects for such an agreement are poor in the near term, as we discuss in the following sections. A political settlement might be more difficult to reach than an armistice agreement since the latter would be narrowly focused on maintaining a cease-fire, not resolving the increasingly deep and broad set of issues disputed between Ukraine and Russia.

The limited available data suggest that political settlements are more durable than armistice agreements.[39] The logic of this is intuitive. A political settlement addresses grievances on both sides and core issues in dispute between them. This leaves fewer issues over which to fight in the future and creates benefits to peace for both belligerents. In the case of the Russia-Ukraine war, a settlement also might open the door to a broader negotiation of rules of the road for regional stability that could mitigate the prospects of conflict breaking out elsewhere along Russia's periphery. Since it is plausible that divergences regarding the security architecture and broader regional order have been a significant driver of Russia's behavior, a negotiated end to the war that addressed those divergences could be more durable.[40]

Therefore, other things being equal, U.S. interests are better served by a political settlement that might bring a more durable peace than an armistice. Additionally, a political settlement could be a first step toward addressing broader regional issues and reducing the chance of a Russia- crisis in the future. If the intensity of competition in Europe is more manageable and the risk of war recurrence in Ukraine is lower, the United States can shift resources in line with U.S. strategic priorities and Ukraine can recover economically with less outside support.[41] However, the level of hostility as of December 2022 between Russia and Ukraine, and between Russia and the West, make a political settlement seem much less probable than an armistice.

Summary

Variation on all of these five dimensions—Russian nuclear use, -Russia escalation, territorial control, duration, and form of war termination—is possible at this stage in the conflict. In the next section, we examine how the United States should prioritize among these dimensions as it formulates its policy toward the war.

Russian President Vladimir Putin chairs a meeting on the restoration of destroyed housing and infrastructure in regions of southwest Russia that border Ukraine, Moscow, February 1, 2023, photo by Sputnik/Mikhail Klimentyev/Kremlin via Reuters

Russian President Vladimir Putin chairs a meeting on the restoration of destroyed housing and infrastructure in regions of southwest Russia that border Ukraine.

Photo by Sputnik/Mikhail Klimentyev/Kremlin via Reuters

Prioritizing the Dimensions of War Trajectories

Since avoiding a long war is the highest priority after minimizing escalation risks, the United States should take steps that make an end to the conflict over the medium term more likely.

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For the United States, the two categories of escalation we have described—Russian use of nuclear weapons and a Russia- conflict—would doubtless be the most-consequential dimensions of possible future war trajectories. Few in Washington would quibble with that assertion. However, there is a vibrant debate about the likelihood that either of these forms of escalation will transpire. As we noted, although the probability of either development is not high, both are plausible due to the circumstances created by the war, and, in light of how profound the consequences could be, avoiding them should remain the top U.S. priority.

Our analysis suggests that duration is the most important of the remaining dimensions for the United States. The negative consequences of a long war would be severe. So long as the war is ongoing, escalation risks will remain elevated. Duration and escalation risks are thus directly linked. Additionally, a longer war will continue to cause economic harm to Ukraine as well as to Europe and the global economy. For the United States, a longer war will entail both increased direct costs (such as more budgetary and military support to Ukraine) and increased opportunity costs in terms of pursuing other foreign policy priorities. More Ukrainians will suffer and the upward pressure on food and energy prices will continue while the war is ongoing. There are possible benefits to protracted conflict: a further weakening of Russia and the opportunity for Ukraine to make territorial gains. But the former no longer represents a significant benefit; Russia has already been weakened dramatically. And the latter is uncertain—more time might allow Russia to make gains—and the benefit of further Ukrainian territorial control, as we will discuss next, is important for the United States but does not outweigh the consequences of a long war.

Greater Ukrainian territorial control would be beneficial for the United States. The humanitarian case is compelling for liberating more Ukrainians from the horrors of Russian occupation. The international order and economic arguments for further Ukrainian territorial reconquest are less clear-cut. Moscow was in violation of the territorial integrity norm since its annexation of Crimea and invasion of eastern Ukraine in 2014. Even a Russian retreat to the pre-February 2022 status quo ante lines would not mitigate that violation. And the United States has tools to increase the costs to Russia for its violation and to deny legitimacy to its illegal occupation. That said, denying Moscow territorial gains would help send a message that similar acts of aggression will result in similarly powerful pushback. Greater Ukrainian territorial control could return economically productive assets to Kyiv's control, decreasing Ukraine's dependence on the United States and its allies. However, given where the line of control was as of December 2022, that economic benefit is unlikely to be essential to Ukraine's viability. If Russia were to push significantly farther west, and particularly if it took control over Ukraine's entire Black Sea coast, the economic impact would likely be severe. But as of December 2022, such an outcome is improbable because Russia's military appears incapable of making significant territorial advances. Conversely, if Ukraine were to rout the Russian military and retake all of its territory, including Crimea, the risks of nuclear use or a Russia- war would spike. That outcome seems equally improbable at the present stage of the conflict.

Our analysis suggests that there are two possible forms of conflict termination in this war. Since territorial reconquest in itself will not end the war, and absolute victory by either side is unlikely, the importance of this dimension rests on how much value the United States would gain from a political settlement versus an armistice agreement. A political settlement may be more durable than an armistice, potentially creating greater stability in Europe and allowing the United States to free up resources for other priorities. That gain would be important, but a durable armistice would also be beneficial to U.S. interests. And a political settlement seems less plausible, at least at this stage of the conflict.

This prioritization of the dimensions of possible war trajectories has direct implications for U.S. policy. Since avoiding a long war is the highest priority after minimizing escalation risks, the United States should take steps that make an end to the conflict over the medium term more likely. By itself, Washington cannot shorten the war. But since the conflict will likely end with negotiations, avoiding a long war requires efforts to spur talks. And the United States could take steps to address key impediments to starting them. The next section identifies impediments that could plausibly be addressed by U.S. policy.

Impediments to Ending the Conflict

Putting aside the question of its desirability, is a negotiated end to the fighting even possible? As of December 2022, it seems highly unlikely in the near term. Russia and Ukraine have not engaged in negotiations on a settlement since May. There are many reasons for this aversion to talks, such as increasingly intractable territorial disputes and domestic political constraints that make compromise difficult. For example, the Ukrainian public may find it difficult to compromise with a country that has committed atrocities and continues to hold Ukrainian territory, especially when the military appears capable of further gains.[42] U.S. policy cannot overcome all such impediments to negotiations.

Given the U.S. interest in avoiding a long war, the question for Washington is whether there are dynamics at work that U.S. policy could plausibly affect. Although there are many factors that lead the parties to continue to fight, the scholarship on war termination suggests two drivers of the parties' resistance to negotiations that Washington could ameliorate. The literature's basic finding is that negotiating an end to a war requires both sides to believe that they have more to gain from peace than from continuing to fight. Optimism about the future trajectory of the war and pessimism about the likelihood and benefits of peace thus inhibit negotiations and drive belligerents into protracted conflicts.[43] In the remainder of this section, we explain why these dynamics may be at work for both Russia and Ukraine. In the following section, we assess the policy instruments available to the United States to address them.

Mutual Optimism About the Course of the War

Both sides believe that their relative power, and thus ability to prevail, will improve over time.

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International relations scholarship has found that wars become protracted when the belligerents disagree about their prospects for victory. In peacetime, states cannot be sure about an adversary's military capabilities or willingness to fight and therefore its ability to win on the battlefield. Moreover, states have an incentive to exaggerate their power and resolve so as to get what they want without having to go to war. Some scholars think of wars as resolving this information problem since fighting reveals the true balance of power and interests. Once that information is clear to both sides, the weaker or less determined of the two should become more pessimistic about what it can gain by continuing to fight. This pessimism should cause that side to adjust its demands downward, potentially opening space for an agreement to end the war.[44]

This theoretical expectation about views converging on which side is more likely to prevail rests on an assumption that power is largely fixed.[45] When this assumption holds, battlefield outcomes should be a reliable indicator of power and therefore a guide to how the sides will fare in future clashes. In theory, both sides should use this information to anticipate future developments, and their expectations about the war's trajectory should converge. But when one side's power fluctuates while the fighting is ongoing, or when its power could change significantly in the future, evidence from past battlefield results will not produce that same clarity. Instead, this variation (or possible future variation) in one side's power can lead belligerents to different conclusions about how the conflict will evolve.[46]

For example, this dynamic appears to have contributed to the length of World War I in Europe. A stalemate on the Western front in 1917 meant that the belligerents, if they were looking at the record on the battlefield, should have agreed that their prospects for victory were roughly even. Instead, both sides appeared to be optimistic about their ability to gain by continuing to fight. The British and French were unwilling to negotiate that winter in part because they hoped that U.S. entry into the war would break the stalemate. Germany believed that, with an end to fighting on the Eastern front after it signed a peace treaty with Russia, redeployed German forces would make a breakthrough in the west. This mutual optimism may have been a factor that inhibited negotiations in late 1917 and early 1918.[47]

In the Russia-Ukraine war, this dynamic may also be at work. Ukraine's power is heavily dependent on an unpredictable outside factor: Western assistance. None of the actors mentioned—not Russia, Ukraine, or the West—anticipated the unprecedented levels of Western military and intelligence assistance to Kyiv, or the effect that assistance would have. None are sure how much aid will be provided or the effect it might have in the coming months and years. To put it in terms of the information problem, it is unclear how powerful Ukraine will be in the future.

In the face of this uncertainty, the two countries seem to have come to different conclusions about Ukraine's future power. As a result, despite months of fighting, both Russia and Ukraine appear to be optimistic about the future course of the war. Ukraine is optimistic that Western support will continue to increase and that Ukrainian capabilities will improve. Russia appears to believe that the United States and its allies will eventually waver in their support for Ukraine, particularly as the costs of the war mount. In part, the Kremlin says that high energy prices, fueled by the ongoing conflict, will strain European economies and cause support for helping Ukraine sustain the fight to diminish. As former President and current deputy chair of the Russian Security Council Dmitri Medvedev put it, "America always abandons its friends and its best [proxies]. It will happen sooner or later this time too."[48] Once it is inevitably deprived of its Western lifeline, Ukraine, according to Moscow, will be unable to prevail against the Russian military.

In short, both sides believe that their relative power, and thus ability to prevail, will improve over time. The centrality of Western assistance to Ukraine's war effort, and the uncertainty about the future of that assistance, has led Moscow and Kyiv to different conclusions about which of the two will gain the upper hand over time. The conflict is therefore not resolving the information problem in the way that the literature leads us to expect; both sides have grounds for optimism about the possibility of making gains by continuing to fight. Historically this kind of mutual optimism has made wars difficult to end.[49]

Pessimism About the Benefits of Peace

Pessimism about the durability and benefits of peace can also contribute to protracted conflict. We focus on two sources of pessimism: (1) the inability of the two sides to credibly commit to uphold agreements and (2) a Russian view that Western sanctions will continue after the war ends, making peace less attractive than it could be.

Fears That Peace Will Not Last

Pessimism about the durability of peace can stem from fear that the other side will not uphold commitments it makes as part of a deal to end a conflict yet. Mistrust, on its own, need not prevent an agreement; belligerents generally do not trust each other after a conflict, yet many wars end through negotiations. The real impediment to negotiations emerges if at least one of the belligerents believes that the other (1) is a determined aggressor that could gain in relative power in the future and violate any agreement once its position improves or (2) could have significantly different preferences in the future. Such concerns, known as credible commitment problems, can lead belligerents to continue fighting even when they know victory is impossible.[50]

Returning to the World War I example: In addition to mutual optimism about continuing the war, credible commitment problems also kept the belligerents fighting despite the stalemate. Fear that Germany would grow in power after the war as it integrated lands acquired through the treaty with Russia led London and Paris to question whether Berlin would uphold an agreement. Therefore, Britain assessed it had to achieve an absolute victory over Germany rather than negotiate an end to the war.[51]

A credible commitment problem is certainly at work in the Russia-Ukraine war. The Ukrainian leadership appears to believe that Russia is a predator state that will abandon any cease-fire once it has reconstituted its military and attack again. Ukraine may also fear that it could lose Western support during any break in the fighting brought about by an armistice or political settlement, allowing Russia's military to recover more substantially or quickly than its own. These fears will affect Kyiv's openness to negotiations regardless of how much territory it controls. Even if Ukraine were to regain control over the entirety of its internationally recognized territory, these same concerns could limit the prospects for ending the war.

An Unappealing Peace

A second credible commitment problem—the possibility of a change in Ukraine's preferences—may be making Russia pessimistic about the benefits of peace. Russia has long sought to ensure that Ukraine remain outside . Earlier in the conflict, Ukraine signaled that it might accept neutrality as part of a settlement.[52] Russia would presumably see a significant benefit to a peace in which Ukraine made a credible commitment not to join . But Russia has little faith that any Ukrainian pledge of neutrality would be upheld. Moscow has experienced shifts in Ukrainian foreign policy and has a dim view of the Ukrainian elite's ability to keep its promises over the long term. Therefore, the Kremlin would be concerned that a future Ukrainian government, which is more deeply committed to  membership, could take power and undo any neutrality pledge made as part of a settlement.

Another factor also may be contributing to Russia's pessimism about the benefits of peace: the prospect of continued Western sanctions after the war. The United States and its allies have imposed unprecedentedly severe sanctions on Russia as a punishment for its invasion of Ukraine. However, it is not clear that the United States and its partners are willing to participate in a multilateral negotiation process in which they would offer Russia a path to sanctions relief. This pessimism may be reinforced by statements from some U.S. officials that one of Washington's goals is to weaken Russia over the long term.[53] Moscow has ample reason to believe that Western sanctions are likely to continue even if it settles bilaterally with Kyiv to end the war.

U.S. President Joe Biden speaks about continued U.S. support for Ukraine at the White House, January 25, 2023, photo by Evelyn Hockstein/Reuters

U.S. President Joe Biden speaks about continued U.S. support for Ukraine at the White House.

Photo by Evelyn Hockstein/Reuters

U.S. Policy Options to Address the Impediments to Talks

The previous section summarized three factors that reinforce the parties' shared aversion to begin negotiations to end the war: mutual optimism about the future course of the war stemming from uncertainty about relative power; mutual pessimism about peace stemming from credible commitment problems; and, for Russia, the lack of a clear path to sanctions relief. These are far from the only impediments to negotiations. However, they are ones that the United States is most capable of addressing with its own policies. In this section, we describe policy options, along with their trade-offs, that are available for Washington to do so. We acknowledge that there are policies that the combatants themselves or other third parties, such as the European Union, could adopt to address these same impediments. For example, combatants could agree to bilateral measures, such as demilitarized zones, to address fears about a return to conflict. The United States could encourage other states to adopt such policies. Here, however, we focus on options that the United States could implement directly.

Clarifying the Future of Aid to Ukraine

A major source of uncertainty about the future course of the war is the relative lack of clarity about the future of U.S. and allied military assistance to Ukraine.

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A major source of uncertainty about the future course of the war is the relative lack of clarity about the future of U.S. and allied military assistance to Ukraine—both arms deliveries and intelligence-sharing. Although the Ukrainian military's capabilities and effectiveness are the primary drivers of its success, external assistance has been a key factor. For example, U.S. and allied long-range, highly accurate, multiple-launch rocket systems provided to Ukraine in summer 2022 caused major disruptions to Russian military logistics and resupply.

Greater clarity about the future of U.S. and allied military assistance could be used for two purposes. First, if a clear, long-term plan were adopted with credible delivery schedules and clear capability implications, it could make Russia more pessimistic about the future of its own campaign. The United States has already taken steps in this direction with the Ukraine Security Assistance Initiative and the establishment of a component of U.S. European Command dedicated to the Ukraine assistance effort. But arms deliveries have not yet become regular, nor is there a transparent long-term plan. Western assistance continues to be calibrated in response to Russian actions, and thus Ukraine's future capabilities are uncertain. Transparent long-term plans with strong domestic and international backing could minimize the unpredictability, though they may also be less responsive to a changing threat environment.[54]

Second, the United States could decide to condition future military aid on a Ukrainian commitment to negotiations. Setting conditions on aid to Ukraine would address a primary source of Kyiv's optimism that may be prolonging the war: a belief that Western aid will continue indefinitely or grow in quality and quantity. At the same time, the United States could also promise more aid for the postwar period to address Ukraine's fears about the durability of peace. Washington has done so in other cases, providing vast amounts of aid to Israel after it signed the Camp David accords and a bilateral peace treaty with Egypt, ensuring that Israel's capabilities exceeded those of its neighbors. Although this example differs in important ways from the Russia-Ukraine conflict, it suggests that the United States does have ways to calibrate long-term aid commitments to reassure close partners about their ability to defend themselves. Doing so in this case while also signaling the limits of wartime assistance could address Ukraine's short-term optimism about continuing the war while increasing its confidence in the longevity of any arrangements to end the fighting.

Linking aid to Ukrainian willingness to negotiate has been anathema in Western policy discussions and for good reason: Ukraine is defending itself against unprovoked Russian aggression. However, the U.S. calculus may change as the costs and risks of the war mount.[55] And the use of this U.S. lever can be calibrated. For example, the United States could level off aid, not dramatically reduce it, if Ukraine does not negotiate. And, again, a decision to level off wartime support pending negotiations can be made in tandem with promises about postwar sustained increases in assistance over the long term.

Clarifying the future of U.S. aid to Ukraine could create perverse incentives depending on how the policy is implemented. Committing to increased wartime assistance to Ukraine to reduce Russian optimism could embolden the Ukrainians to obstruct negotiations, blame failure on Moscow, and gain more Western support. Announcing a decrease or leveling off in assistance to Ukraine to reduce Kyiv's optimism about the war could lead Russia to see the move as a signal of waning U.S. support for Ukraine. If it took this view, Russia might keep fighting in the hope that the United States would give up on Ukraine entirely. Although recognizing that Ukraine is fighting a defensive war for survival and Russia an aggressive war of aggrandizement, the United States would nonetheless have to carefully and dispassionately monitor events and target its efforts to create the intended effect on whichever side's optimism is determined to be the key impediment to starting talks.[56]

U.S. and Allied Commitments to Ukraine's Security

To address the credible commitment problem for Ukraine, the United States and its allies could consider outlining the long-term commitments they are prepared to make to Ukraine's security if Kyiv comes to terms with Moscow.

Security commitments can take many forms, ranging from promises of limited support in wartime to a vow to intervene militarily to defend another country if it is attacked. Providing Kyiv such a commitment could affect Ukraine's decisionmaking about ending the war: It would address Kyiv's concerns about the credibility of Moscow's promises not to attack Ukraine again as part of a settlement.[57] A U.S. security commitment—particularly a commitment to intervene militarily should Russia attack again—would deter Moscow from future aggression, since Russia would be risking war with a much more powerful coalition, not just with Ukraine. Ukraine would be more confident in its security and would have a more stable environment in which to recover economically from the conflict. A U.S. or allied commitment to Ukraine's postwar security could make peace more attractive to Kyiv by not leaving it to depend on Moscow's word.

Early in the war, Kyiv proposed that the United States and other countries provide Ukraine a commitment even more ironclad than those undertaken by Washington toward treaty allies: an explicit vow to use military force if Ukraine were attacked again. (Contrary to popular belief, not even Article 5 of the Washington Treaty commits  allies to use force if another is attacked. Each ally promises to take "such action as it deems necessary" in the event of an attack on another.[58]) The reaction in Western capitals to the proposed commitment was lukewarm at best.[59] U.K. Deputy Prime Minister Dominic Raab stated "We're not going to . . . replicate unilaterally the  commitments that apply to  members."[60] However, some countries were willing to pledge to help Ukraine in other ways if it were attacked again. As one French official said, "It would be military supplies so that [Ukraine] can deal with a new attack or, possibly, [commitments] that would see us get involved if Ukraine is attacked in a way where we could assess how to assist it."[61] A July statement from the Group of Seven (G7) elaborated on these pledges, proposing that  members would engage in intelligence-sharing, resilience, and other measures as part of a "viable post-war peace settlement."[62] The United States and key allies were prepared to commit to the kind of support they are currently providing Ukraine if it were to be attacked again. That support is extraordinary in scale and scope, and Ukraine has used it more effectively than almost anyone imagined before the war. Still, promising to provide this type of support again might not reduce the credible commitment problem for Ukraine: As effective as it has been, the support has not stopped Russia from continuing its aggression. Creative approaches could be considered that are not as binding as U.S. mutual defense treaties but greater than pledges to return to current levels of support in a future contingency.

Although it might help sweeten a deal for Kyiv, a U.S. security commitment to Ukraine might be unpalatable for Moscow. After all, one of the motives for Russia's war was to prevent Ukraine's alignment with the West. The creators of the Istanbul Communique envisioned overcoming this challenge by getting Russian buy-in for a multilateral security guarantee arrangement with Russia, the United States, and others named as guarantors. The guarantee would be made with the understanding that Ukraine would remain neutral and unaligned with any of those powers.[63] The document also ruled out foreign military deployments and exercises on Ukrainian territory. Although Russia's endorsing a U.S. security commitment to Ukraine might seem counterintuitive, it would in this case be on the condition of Ukraine's permanent neutrality and strict limits on foreign military presence on its territory.

The offer of even a limited U.S. security commitment could carry costs and risks for the United States. For example, if the United States were to devote significant resources to arming Ukraine in peacetime, it would have fewer resources for its other priorities. Moreover, in the event of another Russia-Ukraine war, commitments to Ukraine would limit U.S. freedom of maneuver in crafting a response. A more expansive security commitment could lead to a direct clash with Russia in case of a future attack on Ukraine. Therefore, the benefits associated with a U.S. security commitment—Ukraine's increased willingness to negotiate, a possible end to the war, and deterring future Russian aggression—would have to be carefully weighed against these potential drawbacks.

U.S. and Allied Commitments to Ukraine's Neutrality

As noted earlier, the credible commitment problem for Russia relates to a potential Ukrainian neutrality pledge made as part of a settlement. Moscow's perception that Ukraine's unilateral commitment would not be credible could contribute to making peace much less appealing. As part of the Istanbul Communique, Russia would have received an international-legal commitment to Ukraine's neutrality from the United States and several  allies, in addition to Ukraine's own neutrality pledge. A U.S. and allied commitment to Ukraine's neutrality would create a major additional hurdle—a change in Western policy or even law depending on the nature of the commitment—to Ukraine joining  in the future. Such a promise could mitigate the credible commitment problem for Russia.

Thus far, the United States has maintained its prewar policy on Ukraine's future with : rhetorical support for Kyiv's aspirations for membership and a refusal to engage in negotiations that would in any way undermine  open door policy—the principle that the Alliance will consider any application from qualified states in the region—and the related stance that no other state gets a say in that process. As the July 2022 Madrid  summit communique stated, "We fully support Ukraine's inherent right . . . to choose its own security arrangements."[64] Ukraine itself has returned to emphasizing its objective of joining , after suggesting it might be willing to accept neutrality earlier in the war.[65] President Zelenskyy even put his country's application to  on an "accelerated" track following Putin's annexation announcement in September, although the significance of this move is unclear.[66]

Just as Russian acceptance of U.S. or allied security commitments was linked to the neutrality pledge in the Istanbul Communique, Ukraine would likely need security commitments to make neutrality palatable. On its own, a multilateral commitment to Ukraine's neutrality would be seen in Kyiv as a net negative for the country's security: The prospect of  membership would be off the table, with nothing provided in its place. Politically, any government in Kyiv would need something to show to the public as a recompense for "losing" the possibility of joining the Alliance.

As with a U.S. security commitment, a commitment to Ukraine's neutrality would entail trade-offs for the United States. On the one hand, it could help bring about the end of the war and resolve a long-standing source of -Russia tension. But on the other hand, it would be extremely politically difficult at home, with allies, and with Ukraine. Indeed, Kyiv's independent, sovereign decision to formalize its neutrality would be a necessary prerequisite for Washington to contemplate providing a commitment to that status. And even then, some U.S. allies might resist any hint of a change in  open-door policy, particularly one made under Russian pressure. Further, a combined commitment to Ukraine's security and neutrality would be a novel construct for the United States; traditionally, firm security commitments have only been issued to allies. Making Ukraine more secure without undermining its neutrality would be a difficult balance to maintain.

Establishing Conditions for Sanctions Relief

As discussed already, part of Russia's pessimism about peace could be a belief that international sanctions will remain in place even if it negotiates an end to the war in Ukraine. Offering a pathway to partial sanctions relief, therefore, is one step that could make negotiations more likely.[67] The United States, the European Union, and other partners imposed unprecedented sanctions on Russia, including the freezing of more than $300 billion in Russian central bank assets and the imposition of export controls that will severely limit the country's future growth. Thus far, U.S. sanctions have largely been framed as a punishment for Russia's actions, not as a tool to affect Russia's behavior and bring it to the table. As Daniel Drezner has pointed out, the United States and its partners have not been explicit about "what Russia can do to get the sanctions lifted." The "lack of clarity undermines coercive bargaining, because the targeted actor believes that sanctions will stay in place no matter what they do."[68] The promise of sanctions relief contributed to Iran's willingness to negotiate over its nuclear program and conclude the Joint Comprehensive Plan of Action in 2015 and to Libya's agreement to renounce weapons of mass destruction in 2003.[69] Although not perfect analogies, these experiences suggest the plausibility of using the promise of conditional sanctions relief, as part of a package of policies, to influence a rival's calculations.

Some might contend that promising sanctions relief would reward Russian aggression and send a signal to China and other U.S. adversaries that they can make gains by using force. However, this argument ignores the steep price that Russia has already paid for this war: harming its economy, tarnishing its international reputation, weakening its military, sparking European efforts to cease importing Russian hydrocarbons, spurring further  enlargement to Finland and Sweden, and provoking European allies to increase defense spending. Some of these costs may be transitory for Russia, but others—such as  enlargement, European efforts to reduce energy dependence, and economic damage—appear to be permanent shifts.[70] Given these significant costs of the war for Russia, it is less likely that other states will look at the current conflict as clear evidence that aggression pays, even if some sanctions are eventually relieved as part of an agreement to end the war. Furthermore, sanctions relief is likely to be partial at most; some measures, such as the much stricter export controls, are intended to be permanent.

There are other risks to consider, however. The United States has expended considerable effort building and holding together a global coalition to sanction Russia. Presumably, the United States would aim to gain support from members of this coalition before signaling the possibility of sanctions relief to Russia, but it may not be possible to get all members to agree, which could limit the amount of relief the United States could offer. Even if coalition members were unified on a plan for sanctions relief, a risk would remain: As the members of the coalition begin to unwind sanctions as part of a negotiations process, some states might become reluctant to put them back in place if the Ukraine-Russia negotiations or agreements collapse. The coalition may not be as strong as it is now if it later needs to reimpose sanctions. Moreover, U.S. leaders may pay a political cost domestically and with allies opposed to any sanctions relief.

Conclusion

The debate in Washington and other Western capitals over the future of the Russia-Ukraine war privileges the issue of territorial control. Hawkish voices argue for using increased military assistance to facilitate the Ukrainian military's reconquest of the entirety of the country's territory.[71] Their opponents urge the United States to adopt the pre-February 2022 line of control as the objective, citing the escalation risks of pushing further.[72] Secretary of State Antony Blinken has stated that the goal of U.S. policy is to enable Ukraine "to take back territory that's been seized from it since February 24."[73]

Our analysis suggests that this debate is too narrowly focused on one dimension of the war's trajectory. Territorial control, although immensely important to Ukraine, is not the most important dimension of the war's future for the United States. We conclude that, in addition to averting possible escalation to a Russia- war or Russian nuclear use, avoiding a long war is also a higher priority for the United States than facilitating significantly more Ukrainian territorial control. Furthermore, the U.S. ability to micromanage where the line is ultimately drawn is highly constrained since the U.S. military is not directly involved in the fighting. Enabling Ukraine's territorial control is also far from the only instrument available to the United States to affect the trajectory of the war. We have highlighted several other tools—potentially more potent ones—that Washington can use to steer the war toward a trajectory that better promotes U.S. interests. Whereas the United States cannot determine the territorial outcome of the war directly, it will have direct control over these policies.

President Biden has said that this war will end at the negotiating table.[74] But the administration has not yet made any moves to push the parties toward talks. Although it is far from certain that a change in U.S. policy can spark negotiations, adopting one or more of the policies described in this Perspective could make talks more likely. We identify reasons why Russia and Ukraine may have mutual optimism about war and pessimism about peace. The literature on war termination suggests that such perceptions can lead to protracted conflict. Therefore, we highlight four options the United States has for shifting these dynamics: clarifying its plans for future support to Ukraine, making commitments to Ukraine's security, issuing assurances regarding the country's neutrality, and setting conditions for sanctions relief for Russia.

A dramatic, overnight shift in U.S. policy is politically impossible—both domestically and with allies—and would be unwise in any case. But developing these instruments now and socializing them with Ukraine and with U.S. allies might help catalyze the eventual start of a process that could bring this war to a negotiated end in a time frame that would serve U.S. interests. The alternative is a long war that poses major challenges for the United States, Ukraine, and the rest of the world.

Notes

- [1] See, for example, Rose, "What Nixon's Endgame Reveals About Putin's"; Cohen and Gentile, "The Case for Cautious Optimism in Ukraine"; Cohen and Gentile, "Why Putin's Nuclear Gambit Is a Huge Mistake."

- [2] See, for example, Joshi, "Three Scenarios for How War in Ukraine Could Play Out"; "Exploring the Possible Outcomes of Russia's Invasion: A Foreign Affairs Collection."

- [3] "Russia Attacks Ukraine as Putin Warns Countries Who Interfere Will Face 'Consequences You Have Never Seen.'"

- [4] Cameron, "Here's What 'High Combat Alert' for Russia's Nuclear Forces Means."

- [5] "Factbox: Has Putin Threatened to Use Nuclear Weapons?"

- [6] Cooper, Barnes, and Schmitt, "Russian Military Leaders Discussed Use of Nuclear Weapons, U.S. Officials Say."

- [7] Cohen and Gentile, "Why Putin's Nuclear Gambit Is a Huge Mistake."

- [8] Charap et al., Russian Grand Strategy: Rhetoric and Reality, Chapter 5; Charap and Colton, Everyone Loses: The Ukraine Crisis and the Ruinous Contest for Post-Soviet Eurasia.

- [9] Kholodilin and Netšunajev, "Crimea and Punishment: The Impact of Sanctions on Russian and European Economies"; International Monetary Fund, "IMF Survey: Cheaper Oil and Sanctions Weigh on Russia's Growth Outlook."

- [10] For a detailed discussion of this general logic, see, Fearon, "Signaling Foreign Policy Interests: Tying Hands Versus Sinking Costs."

- [11] That said, Ukrainian forces are dispersed, and the target environment is thus not particularly rich for  use.

- [12] Kokoshin et al., Voprosy eskalatsii i deeskalatsii krizisnykh situatsii, vooruzhennykh konfliktov i voin, pp. 60–65.

- [13] Kofman and Fink, "Escalation Management and Nuclear Employment in Russian Military Strategy"; Reach et al., Competing with Russia Militarily: Implications of Conventional and Nuclear Conflicts.

- [14] Sonne and Hudson, "U.S. Has Sent Private Warnings to Russia Against Using a Nuclear Weapon."

- [15] Siebold and Stewart, "Russian Nuclear Strike Likely to Provoke 'Physical Response,'  Official Says."

- [16] Shapiro, "We Are on a Path to Nuclear War."

- [17] Harris et al., "Road to War: U.S. Struggled to Convince Allies, and Zelensky, of Risk of Invasion."

- [18] Frederick et al., Pathways to Russian Escalation Against  from the Ukraine War.

- [19] Reiter, "Don't Panic About Putin: Why Even Desperate Leaders Tend to Avoid Catastrophe."

- [20] Fazal, "The Return of Conquest? Why the Future of Global Order Hinges on Ukraine"; Frederick, "Ukraine and the Death of Territorial Integrity."

- [21] Demirjian, "Milley Tries to Clarify His Case for a Negotiated End to Ukraine War."

- [22] Blattman, "The Hard Truth About Long Wars: Why the Conflict in Ukraine Won't End Anytime Soon."

- [23] Copp, "Weapons Shortages Could Mean Hard Calls for Ukraine's Allies."

- [24] Stein and Stern, "Russia Is Destroying Ukraine's Economy, Raising Costs for U.S. and Allies."

- [25] The Organisation for Economic Co-operation and Development notes that growth was slowing even before the war, but it argues that the shock in energy prices exacerbated this trend. Organisation for Economic Co-operation and Development, OECD Economic Outlook.

- [26] "Russia Is Using Energy as a Weapon."

- [27] Wong and Swanson, "How Russia's War on Ukraine Is Worsening Global Starvation." Food prices were already rising before the war because of the COVID-19 pandemic and the effects of climate change. The International Monetary Fund assesses that the war exacerbated these trends but does not quantify the effect. Georgieva, Sosa, and Rother, "Global Food Crisis Demands Support for People, Open Trade, Bigger Local Harvests."

- [28] The aforementioned consequences of a long war increase the more intense the war is. A long but low-intensity conflict would significantly—but not completely—mitigate those consequences. Historically, years-long conflicts have varied dramatically in intensity. For example, the Iran-Iraq War of the 1980s lasted for nearly eight years and caused about half a million combat fatalities. The conflict in Western Sahara, where the Polisario Front fought against Morocco, has been much longer (47 years) but much less deadly. In Ukraine itself, the violence that persisted from February 2015 to February 2022 in the Donbas pales in comparison with what we see today. It is difficult to anticipate where a possible long war in Ukraine could fall along such a spectrum. On the one hand, limited munition stockpiles and difficulty mobilizing personnel on both sides could eventually reduce the intensity of the conflict. On the other hand, if both Ukraine and Russia—and their respective international partners—remain committed, it is possible for the intensity of the war to remain roughly at current levels for months—perhaps even years.

- [29] Reiter, How Wars End, pp. 3–4.

- [30] Zagorodnyuk, "Ukraine's Path to Victory."

- [31] Lutsevych, "Russia's Retreat from Kherson Brings Ukraine One Step Closer to Victory."

- [32] For example, Saddam Hussein remained in power after Iraq's loss in the Persian Gulf War. Weeks, Dictators at War and Peace, pp. 17–18.

- [33] Cochran, "Will Putin's War in Ukraine Continue Without Him?"

- [34] Fortna, "Scraps of Paper? Agreements and the Durability of Peace."

- [35] Fortna, "Scraps of Paper? Agreements and the Durability of Peace."

- [36] Kreutz, "How and When Armed Conflicts End: Introducing the UCDP Conflict Termination Dataset"; Fazal, "The Demise of Peace Treaties in Interstate War"; Fortna, "Scraps of Paper? Agreements and the Durability of Peace."

- [37] Rustamova, "Ukraine's 10-Point Plan." For more context on the proposal, see Charap, "Ukraine's Best Chance for Peace: How Neutrality Can Bring Security—and Satisfy Both Russia and the West."

- [38] The conflict could also continue indefinitely and gradually fall to a low level of violence without an agreement.

- [39] Kreutz, "How and When Armed Conflicts End: Introducing the UCDP Conflict Termination Dataset"; Fazal, "The Demise of Peace Treaties in Interstate War"; Fortna, "Scraps of Paper? Agreements and the Durability of Peace."

- [40] See Charap, Shapiro, and Demus, Rethinking the Regional Order for Post-Soviet Europe and Eurasia.

- [41] White House, National Security Strategy.

- [42] For a discussion of domestic political dynamics and war duration, see Goemans, War and Punishment: The Causes of War Termination and the First World War; Weeks, Dictators at War and Peace.

- [43] Blainey, The Causes of War; Reiter, How Wars End; Van Evera, Causes of War: Structures of Power and the Roots of International Conflict.

- [44] Blainey, The Causes of War; Reiter, How Wars End. For a discussion of information problems as a cause of war, see Fearon, "Rationalist Explanations for War."

- [45] On the idea that the information problem can change during a war, see Shirkey, "Uncertainty and War Duration."

- [46] Kirshner, writing about prewar assessments, notes that, especially in the face of uncertainty, states can have different interpretations of the available information and make different predictions about how a war will go. Kirshner, "Rationalist Explanations for War?"

- [47] Reiter, How Wars End, pp. 167–168, 173.

- [48] Medvedev, "Nu vot i nachalos'. . ."

- [49] The eventual impact of its September 2022 mobilization is another source of Russian optimism about future military performance. We do not address this factor here because it is not one that can be directly influenced by U.S. policy.

- [50] Reiter, How Wars End.

- [51] Reiter, How Wars End, pp. 166–174.

- [52] "March 15, 2022 Russia-Ukraine News."

- [53] Sanger, Erlanger, and Schmitt, "How Does It End? Fissures Emerge over What Constitutes Victory in Ukraine; News Analysis."

- [54] Making such plans credible to both sides would require congressional support, which could be difficult to attain.

- [55] Such a policy would not be without precedent: The United States has pressured security partners and even allies during wartime in the past. For example, the United States made economic threats against Britain, France, and Israel to persuade them to end their invasion of Egypt in the 1956 Suez Crisis. Pressman, Warring Friends: Alliance Restraint in International Politics.

- [56] Our argument here draws from Crawford's general logic of pivotal deterrence, deterring two states from attacking one another. This type of deterrence involves committing to come to the aid of whichever state is not the aggressor, thus raising the costs of aggression by either party. Crawford, Pivotal Deterrence: Third-Party Statecraft and the Pursuit of Peace.

- [57] Historically, third-party guarantees of this kind have been shown to make negotiated outcomes more likely in civil wars, although evidence of their impact on interstate wars is scant. Walter, Committing to Peace.

- [58] North Atlantic Treaty, Article 5.

- [59] Bertrand, "The US and Its Allies Are Weighing Security Guarantees for Ukraine, but They're Unlikely to Give Kyiv What It Wants"; Malsin, Wise, and Pancevski, "Ukraine Proposal for -Style Security Guarantee Greeted with Skepticism."

- [60] Riley-Smith, "-Style Security for Ukraine Not on Table for Peace Talks, Says Dominic Raab."

- [61] "U.S., Britain, Canada Pledge Artillery for Ukraine."

- [62] " Germany 2022:  Statement on Support for Ukraine." A September proposal prepared by Zelenskyy's administration and former  Secretary General Anders Fogh Rasmussen was broadly similar. Rasmussen and Yermak, The Kyiv Security Compact: International Security Guarantees for Ukraine: Recommendations.  consists of Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States, as well as the European Union institutions.

- [63] Rustamova, "Ukraine's 10-Point Plan"; Charap, "Ukraine's Best Chance for Peace: How Neutrality Can Bring Security—and Satisfy Both Russia and the West."

- [64] , Madrid Summit Declaration.

- [65] Yermak, "My Country, Ukraine, Has a Proposal for the West—and It Could Make the Whole World Safer."

- [66] Khurshudyan and Rauhala, "Zelensky Pushes 'Accelerated' Application for Ukraine  Membership."

- [67] Alternatively, the United States could threaten further sanctions if Russia does not negotiate to increase Moscow's estimate of the costs of war over time.

- [68] Drezner, "What Is the Plan Behind Sanctioning Russia?"

- [69] Maloney, "Sanctions and the Iranian Nuclear Deal: Silver Bullet or Blunt Object?"; Jentleson and Whytock, "Who 'Won' Libya? The Force-Diplomacy Debate and Its Implications for Theory and Policy"; Khalid, "As the Russia-Ukraine War Drags On, What Is the Endgame for Sanctions?"

- [70] On long-term economic consequences of the war, see, Sonin, "Russia's Road to Economic Ruin: The Long-Term Costs of the Ukraine War Will Be Staggering."

- [71] Hodges, "Joe, I think Ukraine will continue with or without WH approval . . ."

- [72] Kupchan, "It's Time to Bring Russia and Ukraine to the Negotiating Table"; Fix and Kimmage, "Go Slow on Crimea: Why Ukraine Should Not Rush to Retake the Peninsula."

- [73] Mauldin, "U.S. Goal in Ukraine: Drive Russians Back to Pre-Invasion Lines, Blinken Says."

- [74] Biden, "President Biden: What America Will and Will Not Do in Ukraine."

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