President Volodymyr Zelensky of Ukraine on Saturday accused President Vladimir V. Putin of Russia of trying to surround Kyiv’s forces in Russia’s Kursk region to improve his position amid cease-fire talks with Washington, but said that Ukraine’s forces had not been trapped.
Russian forces appear close to driving Ukraine from all of the territory it seized in the Kursk region last year — a push that appeared to accelerate after President Trump froze military aid and intelligence support to Ukraine on March 3. The flow of aid resumed last week as Ukraine agreed to a Trump administration proposal for a 30-day cease-fire with Russia.
On Thursday, Mr. Putin said he was open to the proposal but would seek to negotiate over a number of issues.
Here is a look at the Ukrainian incursion — the first on Russian soil since World War II — and how Russian troops are fighting back.
Why is Kursk important?
Kursk is an area of western Russia that borders the Sumy region of Ukraine. Sumy had long been thought to be a place where Russia might try opening a new front in its full-scale invasion of Ukraine, which began in February 2022.
But in a move that surprised even its key allies, Ukrainian troops caught Moscow off guard last summer, pouring across a thinly defended border and opening a new front themselves.
The main objectives, one Ukrainian colonel told The New York Times, were to divert Russian troops from the grueling fighting in the eastern Donbas region of Ukraine, push Moscow’s artillery out of range of the Sumy region and damage Russian morale.
Within weeks of the incursion, Ukraine had established control over a slice of Kursk that its officials said encompassed nearly 500 square miles of farmland and settlements. Though barely a sliver of Russia, the largest country in the world, the assault was an embarrassment for Mr. Putin. It also surprised Ukraine’s allies, including the United States, who had not been told in advance.
The most important town in Kursk that Ukrainian forces seized was Sudzha, an administrative center with a population of around 5,000 people before the incursion.
Analysts said that Ukraine’s offensive was a gamble, stretching its military resources at a time when Kyiv’s troops were struggling to defend a long front line in their own territory.
Mr. Zelensky said that his military did not want to stay on Russian soil indefinitely, and that territory gained in Kursk could be used to strengthen Ukraine’s position in future negotiations with Moscow.
How has Russia responded?
Initially, rather than diverting large numbers of troops to defend Kursk, Mr. Putin said that eastern Ukraine remained Moscow’s main military focus. Russian troops continued their creeping advance within Ukraine, taking the town of Vuhledar in October and then pushing farther west.
Weeks into its incursion in Kursk, Ukraine’s push slowed and its troops began gradually to lose ground as Russian forces deployed there in greater numbers.
Then, in the fall, Russia received a boost from its ally North Korea, which deployed around 11,000 soldiers to Kursk to assist Moscow’s defense. The deployment at first unnerved Ukraine and its allies. But the North Korean troops suffered wave after wave of heavy losses and, for a time, were withdrawn from the frontline.
In recent weeks, Russian forces, assisted by North Korean fighters, have advanced rapidly in Kursk, using drones and fighter jets to retake much of the territory that Ukraine had held.
Ukraine’s top military commander, Gen. Oleksandr Syrsky, pushed back against the idea of an immediate Ukrainian withdrawal from the area. He said that night that Ukrainian troops would “hold the line in the Kursk region for as long as it remains reasonable and necessary.”
The next day, Russia’s Defense Ministry claimed that its forces had retaken the town of Sudzha. The Ukrainian military’s general staff has not publicly commented on Russia’s capture of Sudzha. But on Saturday morning, it released a map of the battlefield showing the town outside Ukrainian-controlled territory in the Kursk region.
Russia’s Defense Ministry said its forces had retaken two villages outside Sudzha, which leaves only small pockets of Russian land along the border under Ukrainian control.
What is the situation now?
In a post Friday on his Truth Social platform, Mr. Trump said thousands of Ukrainian troops were “completely surrounded by the Russian military.” That appeared to be a reference to the Russian claims that Ukrainian soldiers were surrounded in the Kursk region — claims that have been challenged by independent analysts and that Ukraine’s military officials have rejected.
Hours after Mr. Trump’s post on Truth Social, Mr. Putin insisted at a news conference that Ukrainian forces still fighting in the Kursk region to lay down their arms, saying he would spare their lives if they surrendered. He also said Ukrainian forces were encircled there.
Mr. Zelensky, speaking to journalists in Kyiv, called the claim untrue.
“There are Ukrainian troops in Kursk region,” he said. “Their encirclement is Putin’s lie.”
Russia’s forces, however, are trying to cut off and trap Ukrainian troops in the Kursk region by pushing into the neighboring Sumy region in Ukraine, Mr. Zelensky said, adding that Kyiv was countering the threat.
Russia’s increasing ability to strike the road coming out of Sudzha into Ukraine has made withdrawals from the Kursk region perilous for Ukrainian forces, Ukrainian officials said on the condition of anonymity to discuss the battlefield situation. They noted, however, that the troops were not fully surrounded.
It was not clear how many Ukrainian forces remained in the Kursk region as of Saturday, with many of them having withdrawn in recent weeks.
Maria Varenikova and Anton Troianovski contributed reporting.
