A peace settlement to end a major war can be an opportunity to reorder the world. After the defeat of Napoleon Bonaparte in France, European leaders negotiated new territorial boundaries at the Congress of Vienna, in 1814–15, in an attempt to establish a stable balance of power on the continent. At the Paris Peace Conference in 1919, after the end of World War I, participants drew up plans for the League of Nations, an international body tasked with securing world peace. And in early 1945, as World War II was winding down, representatives of 50 countries gathered to draft a charter for a new organization to replace the ineffective league. The United Nations began its operations later that year.

Negotiations to end Russia’s war in Ukraine may not yield a new global security body, but they may well shape the future of international cooperation—and the world is due for reordering. U.S. President Donald Trump has taken a wrecking ball to the institutions and partnerships at the heart of the U.S.-led international system, his tariff threats have brought turmoil to the global economy, and his berating of Ukrainian President Volodymyr Zelensky in the Oval Office in late February dissolved any lingering expectation that the United States would remain a trusted partner to its traditional allies and friends. Beyond the United States, European countries want greater control of their own security, and many other countries are pushing for effective forms of multilateralism that are not dominated by the West. Addressing all these pressures with a sweeping agreement in Ukraine is likely impossible; Kyiv’s and Moscow’s positions are too starkly opposed, and the rest of the world is too fractured. A deal could easily collapse, too. History books are full of unsuccessful attempts at peace, including those in 1938 and 1939 that failed to stop the outbreak of World War II.

Short of a grand scheme, however, a practical peace process that brings in both great powers and frontline states is possible in Ukraine. The settlements of the past offer guidance. Even a partial solution can be effective if it halts the fighting; cease-fires have proved durable in other frozen conflicts, including those negotiated in Korea in the 1950s and Cyprus in the 1970s. A territorial arrangement need not be permanent; Finland ceded territory to the Soviet Union in the 1940s but managed to reclaim small parts of it decades later. A deal in Ukraine must not undermine the credibility of either the Russian or the Ukrainian governments, as post–World War I settlements did to the German government, planting the seeds for World War II. And it must offer security guarantees to Ukraine backed by real force, unlike the weak promises offered to eastern European states in the interwar years.

The result will not be a perfect deal. But if these conditions are all met, an agreement in Ukraine today can maintain peace until the circumstances are more favorable for a durable solution—and it can even provide a template for effective multilateral cooperation in this turbulent new world.

There is reason to want to turn the agreement that ends Russia’s war in Ukraine into a grand bargain. The conflict is connected to hostilities elsewhere, with Iran and North Korea supplying Russia with weapons and North Korea supplying troops. A sweeping settlement could provide a framework for resolving conflicts in Africa, Asia, and the Middle East, as well, by establishing a brand-new security mechanism to address the destabilizing effects of weaponized finance, trade wars, and fractured diplomacy. The model would be the negotiations to end World War I and World War II. These settlements were comprehensive, invoking bold visions of world peace and involving territorial settlements, population movements, security clauses, and financial reparations. Both aimed to eliminate the fundamental causes of the conflicts they ended: in 1919 by encouraging democratization to reduce militarism and in 1945 by demanding the unconditional surrender of the defeated Germany and Japan to end those specific countries’ aggression.

In both instances, the negotiating parties largely agreed on the cause of the war and how it might be eliminated—and they could impose their view on the defeated. This is not true in the case of Ukraine, however, which makes a grand bargain impossible today. The parties do not see eye to eye on what caused the war, and no amount of mediation or external pressure can reconcile their positions.

For Ukraine, the cause of the war is clear. Putin decided to seize and annex Crimea in 2014, stoke low-intensity fighting in the Donbas region thereafter, and eventually launch a full-scale invasion in February 2022. Removing the source of the conflict would mean removing the current Russian government—an unlikely prospect. From Russia’s perspective, the cause of war is very different. Putin has claimed that the government of Ukraine is illegitimate, has violated constitutional norms, and is run by Nazis. He has suggested that security guarantees from the West, in particular the vague promise of eventual NATO membership that Ukraine was offered in 2008, were propping up the Ukrainian state, and he has questioned the basic notion of Ukraine’s existence as an independent state.

Reaching an understanding about the underlying cause of a war is a prerequisite for negotiations on a comprehensive settlement. Without it, trying to get the belligerents in the war to agree on permanent territorial boundaries, how to secure those........

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