Sitting Ducks

One morning last month, two young Russian soldiers were chatting on a hillside in eastern Kosovo, on the border with Serbia, when one of them noticed unusual movements just across a narrow wooded valley. Through his high-powered scope, he spotted a handful of men in sweatsuits and jeans moving briskly around an armored vehicle mounted with a heavy machine gun. Peacekeepers daily see Albanian rebels training across the border, but this group "looked like they were preparing something," recalled Sergeant Sergey Bogoyavlensky, 28, last week at the Russian base a few kilometers away.

Bogoyavlensky had just signaled his commander when the firing...