How Would Peacekeeping Work in Ukraine? These Experts Gamed It Out.

When military and civilian experts on peacekeeping started meeting in Geneva in the spring of 2022, they insisted on discretion. Their topic was sensitive: how to implement a future cease-fire in Ukraine.

Last week, that group of experts went public for the first time, publishing a 31-page paper that delves into the technical details of how a cease-fire along a more than 700-mile front line could be monitored and enforced. The paper was shared last month via another confidential channel: a recurring meeting in Geneva between American, Russian and Ukrainian foreign-policy experts who are close to their governments.

The paper, one of the most detailed templates for a Ukraine cease-fire to have been published, is a sign of how quickly the topic of planning for a cease-fire has gone from a controversial and theoretical exercise to an urgent and practical issue.

France and Britain have raised the prospect of sending thousands of their own troops to Ukraine after the fighting stops, though there is little clarity about what that force’s responsibility would be. Russia has shown no sign of agreeing to such a force, while President Trump has offered few assurances of any American backup to it.

“One of the biggest cease-fire monitoring operations ever will be coming at us very quickly, with no planning thus far of what that would look like,” said Walter Kemp, a specialist on European security who drafted the Geneva group’s document.

Mr. Trump has said he wants a quick settlement and in the last week has taken steps aimed at forcing Ukraine to the negotiating table: Suspending military aid and the sharing of intelligence to Ukraine, while repeatedly saying, with no evidence, that he thinks President Vladimir V. Putin of Russia wants to make a deal.

For most of Russia’s three-year invasion of Ukraine, the possibility of a cease-fire seemed far-off and, some analysts say, a taboo topic. Kyiv and Western leaders sought to keep the focus on the battlefield rather than the complications of an eventual compromise, and were reluctant to speak publicly about the possibility that Ukraine would fall short of victory.

But Mr. Trump’s desire to end the fighting quickly has cast a spotlight on what will happen on the ground if the fighting does end. The previous cease-fire in Ukraine, negotiated in Minsk, Belarus, in 2015, was plagued by spotty monitoring and the absence of a way to punish violations of the deal’s terms.

Last week’s paper, produced by a Swiss government-financed think tank called the Geneva Center for Security Policy, laid out some specific numbers. It proposed a buffer zone at least six miles wide to separate the two armies, and a plan for 5,000 civilians and police officers to patrol it. The paper argued that about 10,000 foreign troops may be needed to provide security for those monitors.

The monitors would report on cease-fire compliance and whether heavy weaponry had been withdrawn an agreed-upon distance from the buffer zone. The mission would operate under a mandate from the United Nations or another international body.

Such a force could help prevent tensions and misunderstandings from spiraling into renewed fighting, but it would be separate from any “tripwire” force meant to provide a security guarantee for Ukraine in the event of another Russian invasion.

Thomas Greminger, the Geneva center’s director, oversaw cease-fire monitoring in Ukraine from 2017 to 2020 as the secretary general of the Vienna-based group doing the monitoring, the Organization for Security and Cooperation in Europe.

He said he pulled together a group of cease-fire experts soon after the 2022 invasion began, to come up with options for how to make a future armistice in Ukraine more durable than the last one.

The experts included officials at international organizations and former military commanders with peacekeeping experience, he said. They requested not to be publicly identified because of the sensitivity of the topic for their institutions.

“We had to be quite discreet,” he said.

Separately, Mr. Greminger hosted confidential discussions between foreign-policy experts from Ukraine, Russia, the United States and Europe.

The participants in those meetings — whose identities Mr. Greminger would not disclose — acted in their personal capacity, he said, though they were expected to be briefed by their governments beforehand and to debrief them afterward. He said the initial purpose of the meetings, which started in 2022, was “to establish a channel of communication” with Moscow, and that scenarios for a cease-fire or settlement were also discussed.

It’s not clear what impact, if any, the cease-fire proposal will have on the negotiations themselves, especially given the personal approach taken by Mr. Trump and Mr. Putin. But the Geneva center’s efforts also shed light on the behind-the-scenes diplomacy that has been a hallmark of a war in which the West and Ukraine have sought to isolate Russia on the world stage while engaging with Moscow on some matters privately.

Back-channel negotiations with Russia, for example, have resulted in a series of prisoner-of-war exchanges and the deal that allowed Ukraine to export its grain through the Black Sea (until Russia pulled out of it in 2023). Throughout the war, the Geneva center’s paper says, Russia and Ukraine “have found ways to cooperate on issues of mutual interest.”

The paper proposes that the international monitors would work with a joint commission made up of both Russian and Ukrainian military officials. Through the commission, both sides could hold each other accountable and negotiate things like the release of detainees, mine clearance and civilian corridors through the buffer zone.

“This is going to be an unprecedented, difficult problem,” said Samuel Charap, a Russia analyst at the RAND Corporation, referring to the implementation of a cease-fire in Ukraine.

One reason is the length of the boundary between Ukrainian and Russian-occupied territory — some five times as long as the Demilitarized Zone between North and South Korea. Another, he said, is the sophistication and range of weaponry available to both Russia and Ukraine.

Mr. Charap said he was not involved with the Geneva center’s project but was familiar with it, and that he was working on his own proposals for how sensors mounted on drones, aerostats, buoys and boats could be used to monitor a cease-fire.

He said that accurate monitoring would be a key factor in whether a future armistice in Ukraine would stick. Increasing the likelihood that a violation would be documented, he said, would reduce the incentives for either side to test the stability of the armistice. It could also lessen the chances that unintentional or rogue actions could trigger renewed fighting.

“I don’t think there is a blueprint that can be easily consulted that is on the shelf” for how to implement a Ukraine cease-fire, said Mr. Charap, who has long called for the West to explore a negotiated settlement. “In part because it was such a taboo issue for so long.”

Skepticism over Mr. Putin’s willingness to agree to a cease-fire, let alone stick to its terms, remains widespread, however; Russian officials pledged almost up until the start of the war that he had no intention of invading Ukraine. And no monitoring mission would be able to deter the Russian president if he decided to launch a new invasion of Ukraine.

Janis Kluge, a Russia expert at the German Institute for International and Security Affairs, a research organization in Berlin, said it was “dangerous to occupy your mind with this illusion” of a potentially imminent cease-fire.

“I don’t think it’s realistic that Russia will agree to something where Ukraine remains independent and sovereign, even in the territory it controls,” Mr. Kluge said.