In 1941, Solow left the university and joined the U.S. Army. Because he was fluent in German, the Army put him on a task force whose primary purpose was to intercept, interpret, and send back German messages to base. He served briefly in North Africa and Sicily, and later in Italy until he was discharged in August 1945. Shortly after returning, he proceeded to marry his girlfriend, Barbara Lewis, whom he had only been dating for six months.