If history tells us anything, it is that ending wars is much more difficult than starting them. This is doubtless true of Russia’s current war against Ukraine, which began in late February 2022. After more than two months of stalemated fighting, the combatants are regrouping for major Russian attacks in the Donbas region. Fighting there is expected to be intense, prolonged, and costly to both sides. Russia also continues to pound away at Mariupol, a city already more than 90 percent destroyed, and to lob periodic salvos at Kyiv in an attempt to distract the Ukrainian government from the attacks in the south and east. At a minimum, Russia’s war aims appear to include creating a land bridge to Crimea and “liberating” Luhansk and Donetsk from total Ukrainian control. Ukraine, in turn, seeks to preserve its regime and control over its sovereign territory, including that populated by a majority of Russian speakers.

How can this war be ended? There are four broad alternatives that could be impacted either by the Russian and Ukrainian leaders, or the world community: (1) one side imposes a decisive military defeat on the other and dictates a postwar arrangement that supports its interests; (2) a protracted military stalemate develops, with graduated commitment of forces and growing casualty lists, leading to pressure for a diplomatic settlement; (3) escalation changes the character of the war dramatically—either horizontal escalation (the war spreads to more countries) or vertical escalation (the use of weapons of mass destruction); or (4) a simultaneous crisis breaks out elsewhere in the world, involving a vital interest for the United States and the international community (for example, China makes an imminent threat against, or an actual attack on, Taiwan).

The first option—a complete capitulation by one side and a decisive victory by the other—seems improbable at this time. NATO can keep pumping weapons into Ukraine indefinitely, and Russia’s diplomatic isolation offers it little in the way of outside support. The tenacity of Ukrainian fighters and their combat skills can be expected to improve with experience. Ukraine, however, is unlikely to be able to impose a decisive victory on Russia that would include the expulsion of the organized Russian military forces from the entirety of Ukrainian territory. Russia’s proximity to eastern Ukraine will ensure that it can continue to keep the region in turbulence should it choose to continue to pay the cost of the war.

Therefore, it follows that the second option—a protracted war followed by a negotiated cease-fire and peace settlement—seems more probable than total victory or defeat for either side. However, for this option to become realistic, adroit diplomacy must enter the equation by NATO, Russia, Ukraine, and effective international mediators. Thus far, diplomacy has taken a back seat to war-making, even though the costs of war have enraged international observers and created a video firestorm of atrocities. Nevertheless, unless and until the combatants and the broader international community take diplomacy seriously, fighting will persist. This broader international community must include representatives from the United Nations, the European Union, the Organization for Security and Cooperation in Europe (OSCE), and selected major powers outside of Europe.

The first objective of diplomatic exchanges among Ukraine, Russia, NATO, and suitable interlocutors should be to get an agreement for a ceasefire in place. This place need not be the final solution to the location of combatant forces but a so-called stop-where-you-are armistice that effectively halts the immediate slaughter. The temporary armistice should be followed by an agreed template for professional diplomatic conferences among representatives of Ukraine, Russia, NATO, and other parties that is acceptable to all sides.

The second objective of diplomacy should be to reach agreement on the political and military end states acceptable to NATO, Russia, and Ukraine. There are two alternative models that might provide a starting point for discussion. One is the Minsk II formula, which would permit limited autonomy for the Luhansk and Donetsk enclaves within a sovereign territorial Ukraine. The other is the Austrian State Treaty of 1955, which provided for that state’s neutrality during the Cold War. In either case, organized Russian military forces would be withdrawn from Ukrainian national territory, and any Ukrainian forces located on Russian soil would also leave. Initially, this might leave partisans and other irregular forces of either side located in hostile territory but contested sectors would be patrolled by international peacekeepers from the UN, EU, or OSCE.

Option three would come into play if either side escalates the war by expanding the fighting into more countries or by introducing weapons of mass destruction into the battlefield. A Russian attack on another country, such as Moldova, or on a NATO member state would call for a forceful NATO response. The war would then be a declaredly NATO-Russian conflict, of which the situation in Ukraine would be only one part. The challenge for NATO would be to maintain in this situation its political unity and collective agreement on military strategy in the face of extended fighting with long-range conventional weapons.

Even more uncertainty would be introduced into option three if Russia were to authorize nuclear first use in Ukraine. Even if the Russians employed only a low-yield weapon fired from a short-or medium-range launcher, the political and psychological effects on Ukraine, NATO, and the international community would be profound—and not entirely predictable. Most governments and their citizens would react with understandable horror. But how should NATO respond to a limited nuclear first use by Russia? In theory, three options would be available: (1) a large-scale military retaliation against targets in Russia with conventional weapons only, accompanied by global diplomacy casting Russia as a historical villain of unprecedented character, as well as a warning that further use of any nuclear weapons by Russia would provoke a NATO nuclear response; (2) a proportionate nuclear response against targets in Russia similar to those destroyed in Russia’s nuclear first use; or (3) a disproportionate nuclear response to Russia against a larger array of Russian military and other targets. Any or all of these options for NATO could be accompanied by unannounced but substantial NATO attacks on Russian space assets and offensive cyberwar.

The challenges to maintaining escalation control and obtaining war termination under option three are considerable—and possibly overwhelming. The Cold War witnessed the deployment of NATO and Soviet nuclear weapons in Europe for many years, but the problem of limiting or ending a nuclear war, once the threshold of nuclear first use had been crossed, proved vexatious to military planners and policymakers. Nuclear weapons as seen by academic theorists might lend themselves to competition in risk-taking or exercises in climbing the so-called ladder of escalation. But Cold War policymakers in NATO and in the Soviet Union were more cautious and dubious about nuclear warfighting even on a “limited” scale. The truth is that, then and now, there was, and still is, no template for fighting and ending a limited nuclear war that was based on experience—only on speculation and wargaming.

Assuming that option three can be avoided, option four presents another potential disruption of efforts to end the war in Ukraine on terms acceptable to both Ukraine and Russia. A Chinese move against Taiwan with the potential to impose regime change would create a second major crisis for U.S. policymakers and their military advisers. Obviously, American military capabilities allow for the management of more than one regional military challenge at a time. But the extent to which U.S. policymakers could focus their attention on deterring or defeating China, while leading NATO efforts to defend Ukraine against Russia, depends on how far both China and Russia are willing to go in their respective military campaigns. A situation in which China is attacking Taiwan, while Russia is simultaneously engaged in horizontal or vertical escalation in Europe, would stress American crisis management and military capabilities to the limit. Congressional confusion and media pandemonium would only increase the difficulty of leaders’ following Rudyard Kipling’s injunction to keep their heads while everyone else was losing theirs.

In conclusion, it may appear that diplomacy is a hard sell with respect to the settlement of the war in Ukraine. But the alternative—continued fighting with the possibility of geographical expansion and/or increased lethality—is worse. And if Chinese and Russian aggression should occur simultaneously, all bets are off.

Stephen J. Cimbala is a Distinguished Professor of Political Science at Penn State University, Brandywine.

Lawrence J. Korb is a senior fellow at the Center for American Progress and a former Assistant Secretary of Defense.

Image: Reuters.