In 1936 Leo Meyer joined the New York National Guard 102nd Engineer Regimental Field Music as a bandsman through the NYNG Cadet Corps. In October 1937 he enlisted into Company ‘B’, 102nd Engineer Regiment and by May 1940 he had been promoted to corporal. In October 1940 he was called, with his unit, the 27th Division, to federal service for 12 months training. From December 1941 to December 1942 Meyer served in the Pacific Theater of Operations as a master sergeant in the positions of Regimental and Battalion Sergeant Major. In March 1943 he graduated from the US Army Air Forces Officer Candidate School. In 1944 he volunteered for service in the infantry and in June 1945 was serving as a lieutenant in Company ‘A’, 34th Infantry, 24th Infantry Division in the Philippines. Meyer earned his first Combat Infantryman Badge during Operation VICTOR V in the Southern Philippines Campaign.