Following the war, Watson served as commander of the International Military Tribunal Command in Germany, where he worked to enhance security and ensure that none of the Nazis on trial for war crimes were able to escape. His later assignments included command of Sixth United States Army's Southern District, command of Fort Lewis in Washington state, chief of Civil Affairs for the U.S. Far East Command, and commander of US Defense Advisory Group, Japan. In early 1953 he was promoted to major general, and he retired later that year.