Asked in December 2025 what the biggest obstacle was to negotiating peace in Ukraine, US President Donald Trump got straight to the point: territory. “Part of that territory has been confiscated. Part of that territory could be made available to those who want it,” he added.
From the very beginning of the large-scale war, Ukrainian President Volodymyr Zelensky ruled out ceding territory to the Russian invaders.
However, when the war in Ukraine finally stops, it seems likely that Russia will control vast swaths of Ukrainian territory in the south and east – around 20% of Ukraine’s territory by 2014, if the current line of control is anything to go by.
Ukrainians have been trying for years to expel Russian forces from occupied areas in the administrative regions of Luhansk, Donetsk, Zaporozhye and Kherson. Captured and fortified by Russia in 2014, Crimea has been virtually out of reach. But despite kyiv’s best efforts, Russia is now poised to seize even more Ukrainian territory if the war does not end soon.
The pressure on Zelensky to accept some kind of territorial loss increases with each new peace plan presented, all of which include some degree of redrawing the map in Russia’s favor. And although the majority of the Ukrainian public opposes the idea of exchanging territory for peace, Western pragmatists, and even some within Ukraine, accept that this will almost certainly be part of any peace agreement.
And then what? If Ukraine accepts the de facto loss of its eastern oblasts as the price of peace, should Ukrainians understand this as a permanent or temporary concession? In the latter case, what measures, if any, are in place for Ukraine to finally restore its territorial integrity?
As an international security expert, I would argue that it is essential that Ukrainians and their international allies have clear answers to these questions now, before a peace agreement is signed.
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Territory lost forever?
History can offer a useful, if imperfect, guide to what happens when states are forced to cede territory to invaders.
Precedents suggest that Ukraine must be prepared for the worst: occupied territories, once lost, often remain so indefinitely. This is what happened when the Soviet Union conquered the province of Karelia from Finland after the Winter War of 1939-1940. Finland attempted to recapture Karelia from Moscow by military means in the Continuation War of 1941-1944. But the Finnish forces were eventually repelled.
Moscow subsequently ordered the mass expulsion of ethnic Finns and implemented a program of political and cultural assimilation. Today, ethnic Russians make up more than 80% of Karelia’s population.
Support for Finland’s reabsorption of Karelia is weak. When asked about this idea 20 years ago, most Finns were reluctant to consider the cost of integrating poor Russian-speaking communities into their prosperous nation-state.
The same could happen with the occupied territories in eastern Ukraine. Over time, Russian-controlled areas could Russify to the point that they are no longer recognizably Ukrainian. In Crimea, for example, since 2014, Russia is believed to have moved more than 200,000 Russian citizens into the territory, in addition to expelling ethnic Ukrainians.
Even if they are not forcibly removed, civilians loyal to kyiv in the occupied areas could choose to leave, and millions already have. But doing so means abandoning property to ethnic Russians, and once ceded, the chances of a permanent return become much more difficult. Ukrainians who remain will face almost certain repression.
As the occupation drags on, the social and economic differences between Ukraine’s ceded territories and free zones will likely become increasingly stark. And this will be especially true if Ukraine joins the European Union, something kyiv has long desired and which could be an incentive for any peace deal involving the loss of territory.
With fewer pro-European Ukrainians living there and a wider cultural gap, the prospect of taking back Russian-controlled provinces could become noticeably less attractive to Ukrainians than it seems today.
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Diplomacy and war: dead ends
Still, Ukrainians could hope to avoid this outcome by acting quickly to dismantle the occupation before it becomes irreversible. In theory, they could achieve this in two ways: through agreements or through fighting. But in practice, neither is likely to work.
Examples of negotiated and voluntary return of territory are scarce. In 1979, Egypt managed to negotiate the return of the Sinai Peninsula, which Israel had captured during the Six-Day War in 1967. Although some in Israel wanted to keep the Sinai for security reasons, Israeli leaders decided to exchange the territory in exchange for a lasting peace with Egypt, a leading Arab nation, in the hope that others would follow suit.
The problem for Ukraine is that kyiv has very little to offer Russia in exchange for the lost territories. If the current war ends, it will likely be on terms favorable to Moscow, which is why territorial concessions are being considered to begin with.
If Ukraine cannot negotiate the return of the occupied territories as part of a peace agreement, it probably means that it will also not be able to negotiate their return in the post-peace phase.
What about the possibility of recovering the territories occupied by force? Finland tried it in Karelia and failed. But other countries have been luckier: France regained Alsace-Lorraine from Germany after World War I, for example. However, it was a change of course that took almost 50 years to come to fruition: Germany had annexed the territory in the Franco-Prussian War of 1871.
Given the huge disparity in size, population, and troop numbers between Russia and Ukraine, it is highly unlikely that Ukraine could regain the territories through war, especially since its international allies would likely refuse to support kyiv in a war of its own choosing against nuclear-armed Russia. The task would be further complicated if Russia managed to include some form of Ukrainian disarmament, or a reduction of its army, in any peace agreement.
*Peter Harris is an associate professor of Political Science at Colorado State University.
This text was originally published in The Conversation
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