The reclaimed area was all farmland and village until the Japanese government bought a large portion of it in 1938, with the view of establishing a naval air station. They commissioned the new base July 8, 1940. When World War II started, the Iwakuni air station was used as a training and defense base. The station housed 96 trainers and 150 Zero fighter planes on the airstrip. In September 1943, a branch of the Etajima Naval Academy was established here, with approximately 1,000 cadets undergoing training in the Basic, Junior and Senior Officer's schools at any one time. American B-29's bombed Iwakuni in May and August of 1945, concentrating on the oil refinery and Rail Transport Office or train station areas. The last air raid took place just a day before the war was brought to a close.
The first allies to reach Iwakuni at the war's end were a group of U.S. Marines who had signed papers ending the conflict for the Japanese air base. After the end of World War II, various military forces from the United States, Britain, Australia, and New Zealand occupied the base. It was designated a Royal Australian Air Force Base in 1948.
When the Korean Conflict started in 1950, units from the Royal Navy and U.S. Air Force arrived at Iwakuni as U.N. forces. Jets flew daily to support front-line troops in Korea, returning each evening to refuel and rearm. The troop processing center located here throughout the war earned Iwakuni the title “Gateway to Korea.”
The U.S. Air Force took command of the station April 1, 1952. During its period of command, the Air Force did much to improve the base's facilities. The U.S. Navy took over the station October 1, 1954. Naval Air Station Iwakuni was greatly enlarged in July 1956 when the 1st MAW moved its headquarters here from Korea. A whole new area was procured on the North side of the station to make room for approximately 2,500 incoming Marines.
The Marine Corps first took control of the installation as Marine Corps Air Facility Iwakuni in 1958. The station, which is just over 1,300 acres, was officially designated as MCAS Iwakuni in 1962. Its mission includes support of operations, maintenance and supply of tenant units and ships.