Grange was commissioned as an infantry officer in December 1969. Grange first saw significant combat action as a second lieutenant assigned to the 101st Airborne's "Lima" Ranger company in the I Corps Tactical Zone of Vietnam in 1970. This unit was part of the 75th Infantry (Ranger) and attached to the 2/17th Cavalry. As a first lieutenant serving a second tour in Vietnam from 1971 to 1972, Grange was an adviser to the Army of the Republic of Vietnam Airborne Division. Grange was awarded multiple Silver Star awards for heroism in Vietnam including his third award for gallantry in action in February 1972 while serving with the U.S. Airborne Advisory Detachment. Grange returned to Fort Bragg in 1972 and served with the 3rd Battalion, 5th Special Forces Group as detachment executive officer and detachment commander until 1974. That year, Grange completed Flight training and subsequently served with the 158th Aviation Brigade. From July 1978 to 1980, Grange served as infantry company commander, C Company, 1st Ranger Battalion, 75th Ranger Regiment, which supported Operation Eagle Claw in April 1980. In 1981 Grange completed the grueling British SAS Course at Hereford, England then attended the Marine Corps Command and Staff College. In 1982, Grange volunteered for and received assignment to the 1st Special Forces Operational Detachment – Delta (1st SFOD-D), or Delta Force at Fort Bragg, North Carolina. Grange commanded B Squadron during the invasion of Grenada in October 1983 followed by service as unit operations officer. In 1987 Grange volunteered for service in South Korea and took command of the 1st Battalion, 503rd Infantry Regiment, 2nd Infantry Division until 1988. He was then assigned as special-operations officer with Special Operations Command, Washington, D.C. in 1989. Grange attended the National War College and returned to Fort Bragg in June 1990 as deputy commander of Delta Force, in which job he commanded a task force during Desert Storm.