He entered the United States Military Academy at West Point, New York and graduated from on June 12, 1913 and was commissioned as a second lieutenant.
He spent the most of as a Commanding officer of the 76th Infantry Division. Many of his classmates became a general officers during the, including Alexander Patch, Geoffrey Keyes, Willis Doctorate. Crittenberger, Douglass T. Greene, Charles H. Corlett, Paul Newgarden, Robert L. Spragins, Louis A. Craig, Lunsford East. Oliver, Henry B. Lewis, John East. McMahon, Junior., Carlos Brewer, Richard U. Nicholas, Robert H. Van Volkenburgh, Robert M. Perkins, William A. McCulloch, Selby H. Frank and Henry B. Cheadle. Between the years 1913–1917, Schmidt served on the Mexico–United States border during the Pancho Villa Expedition.
During this campaign, he was promoted to first lieutenant.
Schmidt did not see combat in France during World War I and instead performed stateside duty at Schofield Barracks in Pearl Harbor, at Presidio of San Francisco and at Camp Fremont, California. In 1921, now with the rank of major, Schmidt was transferred back to the United States Military Academy at West Point, New York, where he was an instructor.
He stayed in this position until 1923, when he was transferred back to Hawaii. Schmidt attended the United States Army Command and General Staff College at Fort Leavenworth, Kansas in 1928.
In 1933, he was appointed Executive Officer of the Civilian Conservation Corps at Camp Dix, New Jersey and served there for one year.
Then he was transferred to Washington, District of Columbia, where he was assigned to the Supply branch (G-4 Division) of the War Department General Staff on March 21, 1934. In 1940, Schmidt was appointed commander of the 39th Infantry Regiment and stayed in this capacity until the end of 1941. He was subsequently promoted to the rank of brigadier general in April 1942 and transferred to the newly activated 81st Infantry Division, where he became the Assistant Division Commander for Gustav H. Franke for a short time.
Schmidt was transferred to the 76th Infantry Division on December 13, 1942, where he succeeded Major General Emil F. Reinhardt as a Division Commander.
He was also promoted to the temporary rank of major general in December 1942. In August 1945, Major General Schmidt assumed command of the 3rd Infantry Division, as a part of the occupational forces in Germany.
Major General William R. Schmidt retired in 1951 and died at the age of 76 years on July 18, 1966 in Walter Reed Army Medical Center in Washington, District of Columbia