NOVOTROITSKE, Ukraine — The battalion commander made a left turn in the trenches and walked into a cramped, pitch-black den. Strips of cloth lined the walls and ceiling. He pulled back a flap. Midmorning light streamed in, allowing the day’s first look at the enemy down below.
Ukrainian government forces have the strategic high ground in this position along the demarcation line in their eight-year conflict with Russia-backed separatists. Oleksander, the battalion commander, warned that the observation window can’t be left open for too long. The separatists might notice and target it.
“Whatever Russia does or doesn’t do, we’re watching,” he said, referring both to the current standoff with separatists and a potential war with their Russian backers. Like other members of Ukraine’s armed forces interviewed for this story, Oleksander offered only his first name and rank,…

