[G]athered in a basement on a quiet, tree-lined street, the Belarusians preparing to leave Warsaw to join the Ukrainian army look more like a bunch of computer programmers getting ready for a long car trip. Maybe that’s because they are a bunch of computer programmers—or anyway, some of them are—gathered in a basement on a quiet, tree-lined street, getting ready for a long car trip...If they are identified, members of their families could be visited, harassed, even arrested by the Belarusian police. “Our relatives are hostages,” one of them told me. Already, mothers of Belarusian soldiers fighting in Ukraine have...