On January 1, 1948, Cates was sworn in as the 19th commandant of the Marine Corps and promoted to the rank of general. He served as commandant for four years, and fought the budgetary erosion of the Fleet Marine Force. As Commandant, Cates continued the push to enlarge the Corps standing forces, eventually getting legislation placing the Corps active strength at three divisions and three air wings, and he brought the first helicopters into service on a test basis of the "new concept" in the Korean War—the usage of which would make an impression on the Commander of the FMF, Pacific, his eventual successor as commandant General Lemuel C. Shepherd, Jr.. Shepherd and Cates would revive the amphibious assault at Inchon.