A small band of Ukrainian soldiers was trapped. They were holding the line on the battlefield, but Russian forces had managed to creep in behind their trench and encircle them.

“Even if the position holds, supplies — ammunition, provisions — eventually run out,” Capt. Viacheslav, the 30-year-old commander of an elite drone unit, said last week as he monitored events from an outpost a few miles away in eastern Ukraine. “Any vehicle attempting to reach these positions will be ambushed.”

“We are always getting stuck in these kinds of tough situations,” he said.

As the war in Ukraine enters its fourth winter and the first snowfall blankets cratered fields strewed with bodies, the situations are only growing tougher for Ukrainian forces.

Gen. Oleksandr Syrsky, Ukraine’s top military commander, recently said his forces were fighting to hold back “one of the most powerful Russian offensives from launching a full-scale invasion.”

Ukraine got a boost on Sunday when the United States, after months of pressure from Kyiv, said it had granted permission for Ukraine to use American-provided weapons to fire deeper into Russia. On Tuesday, they used American-made ballistic missiles, called ATACMS (for Army Tactical Missile System), in an attack on a munitions depot in Russia.