After being commissioned as a second lieutenant after participating in the Reserve Officers' Training Corps program at the University of Wyoming, Schoomaker went to the United States Army Armor School at Fort Knox. He soon became a Reconnaissance Platoon Leader and Rifle Company Commander with 2nd Battalion, 4th Infantry, and a Cavalry Troop Commander with 1st Squadron, 2nd Armored Cavalry Regiment in Germany. He then served in Korea as the S-3 of 1st Battalion, 73rd Cavalry, 2nd Infantry Division. From 1978 to 1981, he commanded a squadron of the 1st Special Forces Operational Detachment – Delta (1st SFOD-D), commonly known to the public as "Delta Force", at Fort Bragg, North Carolina. Following a year at the army's Command and General Staff College at Fort Leavenworth, Kansas, Schoomaker served as the Squadron Executive Officer, 2nd Squadron, 2nd Armored Cavalry Regiment in Germany. In August 1983, he returned to Fort Bragg, to serve as Special Operations Officer, J-3, Joint Special Operations Command. From August 1985 to August 1988, Schoomaker commanded another squadron of the 1st SFOD-D. Following the National War College in Washington, D.C., he returned to command Delta Force from June 1989 to July 1992. Subsequently,