What remains of nine Russian lives lies in body bags and on plastic sheets spread out in a sunny field in eastern Ukraine. Among the bones are a few belongings: passports, dog tags, phones, cigarette lighters, a little money and several pocket-sized prayer cards of Orthodox icons that some believers think bestow protection. The bodies were brought off the battlefield by Oleksiy Yukov and other volunteers from Platsdarm (Bridgehead), a volunteer group whose members risk their own lives to retrieve fallen Ukrainian and Russian soldiers and help return them to their families. Yukov has spent much of his life on...