Natalia Kruglova last spoke to her husband, Pvt. Ivan Petrov, on Sept. 29. The Russian army conscript told Kruglova he had been ordered back to the front lines in southeastern Ukraine. Then he disappeared. Kruglova wrote to her husband’s commanding officers, the Defense Ministry and even military prosecutors in search of news, but to no avail. Weeks later, the army declared Petrov missing but offered no explanation of what had happened to him. “It’s as if no one owes you anything, no one cares,” Kruglova, 45, said in an interview from her home in the Russian far eastern city of...