John Adams Wickham, Jr., was born in Dobbs Ferry, New York on 25 June 1928. He graduated from the United States Military Academy in 1950, was commissioned a second lieutenant, and assigned to the 18th Infantry. He was soon transferred to the 6th Infantry in Europe, where he served until 1953. In 1951, he was promoted to temporary first lieutenant. Two years later he graduated from the infantry and airborne officer courses at the Infantry School. From 1953 to 1954, he served as a platoon leader and executive officer in Company L, 511th Airborne Infantry. He then served with the 37th and 10th Infantry.
In 1954, Wickham was promoted to temporary captain. He attended Harvard University until 1956 to earn degrees in public administration, politics, government and economics. He also married Ann Lindsley Prior in 1956. From 1956 to 1960, he taught at West Point. In 1959, Wickham was made a temporary major. In 1961, he graduated from the Command and General Staff College; then he served a tour with the 1st Battle Group, 5th Cavalry, in Korea. Wickham graduated from the Armed Forces Staff College in 1963. That year he received a promotion to temporary lieutenant colonel. From 1964 to 1966, Wickham served as an aide to General Harold K. Johnson, the Army Chief of Staff. In 1967, he graduated from the National War College.
During the Vietnam War, Wickham led the 5th Battalion, 7th Cavalry, 1st Cavalry Division (Airmobile). He was wounded and recovered in Walter Reed Medical Center in Washington, D.C. In 1968, he was made a temporary colonel. From 1969 to 1970, Wickham led the 1st Brigade, 3d Infantry Division, United States Army, Europe, and then was assigned in the Office of the Joint Chiefs of Staff. From 1971 to 1973, he served as the deputy chief of staff for economic affairs in the U.S. Military Assistance Command, Vietnam. In 1972, he was made a temporary brigadier general. In 1973, he served with the Four-Party Joint Military Commission in Vietnam, and was promoted to temporary major general in the same year.
General Wickham served as an aide to the Secretary of Defense from 1973 to 1976. He commanded the 101st Airborne Division (Air Assault) until 1978. That year, he was promoted to temporary lieutenant general. From 1978 to 1979, he directed the Joint Staff, Organization of the Joint Chiefs of Staff. Wickham was made a temporary general in 1979; he then served as the commander in chief of the United Nations Command and led the United States Forces and Eighth Army, Korea, until 1982.
Wickham returned to the United States to serve as vice chief of staff of the Army until 1983. He then served as Army Chief of Staff from 23 July 1983 to 23 June 1987. As the Chief of Staff, Wickham increased force strength to 18 regular divisions and 10 reserve divisions, and urged measures to care for Army families. He retired from active service in 1987.