DNIPROPETROVSK, Ukraine—Leaning over a map of eastern Ukraine on his desk, Gennady Korban gripped a ballpoint pen and drew a squiggling blue line down its center.
The border, he said, marked the battlefront in his country's war with pro-Russia separatists. One side was stable, rid of "troublemakers," he said. On the other are "maniacs," he said. "Men without families, who don't want families, they just like...