Williams served as a Naval Aviator during World War II and the Korean War. Unlike many other major league players, he did not spend all of his war-time playing on service teams. Williams had been classified 3-A by Selective Service prior to the war, a dependency deferment because he was his mother's sole means of financial support. When his classification was changed to 1-A following the American entry into World War II, Williams appealed to his local draft board. The draft board ruled that his draft status should not have been changed. He made a public statement that once he had built up his mother's trust fund, he intended to enlist. Even so, criticism in the media, including withdrawal of an endorsement contract by Quaker Oats, resulted in his enlistment in the U.S. Naval Reserve on May 22, 1942.