Last Known Activity Service in the Army in World War II; spent five years in the Medical Corps of the Army, reaching the rank of captain. As a medical administrative officer, a duty that sent him to various locations like Hawaii, Casablanca and France. It was in France that he began showing his acting talent by performing in a show to entertain the recovering troops.
Wallach served as a staff sergeant in Hawaii in a military hospital in the United States Army in World War II. He was soon sent to Officer Candidate School (OCS) in Abilene, Texas to train as a medical administrative officer. He graduated as a Second Lieutenant and was sent to Madison Barracks in upstate New York. He was promptly shipped to Casablanca and, later in the war, to France. It was there that a superior discovered his acting history and asked him to form a show for the patients. He and other members from his unit wrote a play called Is This the Army?, which was inspired by Irving Berlin's This is the Army. In the comedic play, Wallach and the other men clowned around as various dictators, with Wallach portraying Adolf Hitler, the leader of Nazi Germany.