Walls rattled and pieces of plaster fell from the ceiling of a basement converted by Ukrainian troops into a forward outpost. Russian shells hit again and again the crumpled building above. Images on a surveillance monitor, linked to a camera outside in the deserted village, showed plumes of black smoke rising all around the compound. “The Russians are very angry today because yesterday we killed two of their tanks,” said Marian, a platoon leader in the volunteer Carpathian Sich battalion deployed on the front line near the Russian-held Ukrainian city of Izyum. Like most military personnel, he is only allowed...