When the Air Corps separated from the Army in 1947 to form its own branch, the United States Air Force, Vann chose to remain in the Army and transferred to the infantry. He was assigned to Korea, and then Japan, as a logistics officer. When the Korean War began in June 1950, Vann coordinated the transportation of his 25th Infantry Division to Korea. Vann joined his unit, which was placed on the critical Pusan Perimeter until the amphibious Inchon landing relieved the beleaguered forces.