General Monteith attended the first class of the new Air Command and Staff School at Maxwell Air Force Base, Ala., in 1946. Graduating in June 1947, he was assigned to the school staff and in June 1948 became operations division chief. In August 1950 he was assigned to the U.S. Element, NATO Planning Group in Paris as chief of the Air Section. Later the same year he was detailed as one of 10 officers in the SHAPE Advance Planning Group. The next year he was detailed as air officer on a team of four who worked directly under Field Marshal Montgomery for development of NATO CPX-1, which was held in April 1952 and attended by all of the top commanders in NATO and the national chiefs of staff. He was then designated as U.S. deputy Standing Group liaison officer with the NATO Council, Palais de Chaillot, Paris. For a year he coordinated Standing Group participation in the first NATO annual review of force requirements conducted under the newly organized NATO Council and Secretariat.
Returning to the United States in 1953, he was air officer on a team of three, working directly for Admiral Arthur Radford, chairman of the Joint Chiefs of Staff. In June 1955 he was reassigned to Headquarters U.S. Air Force as deputy Air Force member of the joint Strategic Plans Committee.
He graduated from the National War College in 1957 and was appointed as commander, 3535th Navigator Training Wing, Mather Air Force Base, Calif., where he commanded the school for radar-navigation-bombardment crewmembers. He assumed duties as chief of staff, Air Training Command, in July 1959 and in September 1961 became commander of the Amarillo Technical Training Center.
General Monteith assumed duties as the senior Air Force member of the Weapons System Evaluation Group, Office of the Secretary of Defense, Washington, D.C., in August 1964, and became manager of Project Cloud Gap in September 1966, a joint endeavor of the U.S. Arms Control and Disarmament Agency and the Department of Defense.
He assumed duties as commander, Lowry Technical Training Center, in August 1967.
He departed for India with the 20th Bomber Command in April 1944 as operations staff adviser and flew in the first heavy bombardment mission against Japan, striking Yawata, Kyushu, on June 15, 1944. In July 1944 he became commander of Forward Echelon, 20th Bomber Command in China, where B-29 strikes against Japanese targets and Okinawa were flown. He directed the withdrawal of the 20th Command Forces from China for regrouping in India in January 1945. At that time he negotiated with Mao Tse-tung and Marshal Chu Teh in Chinese Communist headquarters in Yenan for continued assistance to downed B-29 crews.
In February 1945 as chief of staff of the 58th Bombardment Wing, General Monteith led the wing's advance echelons to Tinian in the Mariannas for initial indoctrination in operations there. He assumed command of the wing in September 1945, and supervised its return to the United States.