KYIV, Ukraine — It was Christmas Day, and four fighters from a volunteer Ukrainian special forces team had slipped over the border into Russian territory. They were on a mission to scout enemy positions, place mines to blow up Russian military equipment and engage in sabotage operations to undermine Moscow’s invasion of Ukraine.
The four soldiers were killed soon after they entered Russia.
It was the type of operation that Ukraine undertakes regularly, covert incursions that bring the war to Russia in small ways, though the Ukrainians rarely talk about them openly.
This time, as the fighters were buried on Tuesday at a crowded funeral at St. Michael’s Golden-Domed Monastery in central Kyiv, their fellow soldiers were eager to talk, praising their comrades and offering a rare glimpse into a shadow war that has been playing out for months, with Ukrainian forces seeking out targets inside Russia itself.
“The enemy must always be in tension,” said a soldier named Marat, 51, a member of the battalion who has engaged in clandestine operations. “It is important for us to bring the war to the enemy’s territory.” The New York Times is identifying the soldiers by first name only, for security reasons.
The bodies of the four soldiers were returned to Ukraine in exchange for the bodies of dead Russian soldiers.
The exact cause of death for the four was still being determined. The bodies were riddled with bullets, and one was still wearing a tourniquet. It remained unclear if the soldiers had stumbled into a minefield and were shot later, had died in a shootout or were executed in some fashion, according to the leader of the battalion, identified by his call-sign, Borghese. Some members of the volunteer battalion said they believed the four were killed after refusing to surrender.
“The Russians deliberately mutilated the bodies,” Borghese said.
Despite the extraordinary danger of cross-border missions, members of the Bratstvo battalion — which means “brotherhood” — said the risks were worth it because Russian forces involved in the destruction of Ukraine should not feel safe anywhere.
For months, ammunition depots, fuel storage facilities, railroad tracks and other industrial targets inside Russia related to Moscow’s war effort have been blowing up in seemingly mysterious explosions.
The Ukrainian military has largely stuck to a policy of strategic ambiguity when it comes to strikes inside Russian territory, neither confirming nor denying any role in such attacks.
The fighters have been identified as Yuriy Horovets, 34; Maksym Mykhaylov, 32; Taras Karpyuk, 39; and Bohdan Lyagov, 19.
A member of the battalion, Vladyslav, 22, has gone on missions in occupied parts of Ukraine and inside Russia itself. Attacking in Russia rather than Ukraine, he said, is less dangerous in some ways, because the occupied territory inside Ukraine is now covered in land mines and Russian soldiers are everywhere. The Times witnessed two of the Bratstvo operations behind the enemy lines in an occupied region of southern Ukraine in November, a mission that included two of the soldiers killed in Russia.
Vladyslav said he could not go into detail about specifics of the large-scale operations other than to say they can include trying to destroy bridges, airfields, oil depots and other targets in Russia and Russian-occupied parts of Ukraine.
He recalls feeling pride the first time he was asked to go on a mission across the border. He declined to go into detail about that mission but said his first thought was: “Finally.”
He was with the four soldiers shortly before they died and recalled that they were excited for the operation.
“They went to the mission on Christmas night, and the next afternoon, it was already known they wouldn’t be back,” he said.
Andriy Kovaliov, a spokesman for the Ukrainian General Staff, which is responsible for overall military strategy, confirmed on his personal Facebook page that one of the soldiers, Mr. Horovets, died a “heroic death” during a combat mission “on enemy territory.”
Ukrainian officials have grown increasingly bold in saying that they reserve the right to strike military targets inside Russia to protect Ukrainian cities and towns, even if they rarely comment on individual reports. Ukrainian special forces on Monday took credit for destroying an unmanned observation tower in Russia’s Bryansk region using a drone strike.
Carlotta Gall and Daria Mitiuk contributed reporting.