During the Korean War, it took part in Operation Chromite, the landings at Inchon, where it had the 1st Marine Division, the 7th Infantry Division and other US Army units under its command. The embryonic planning group for Chromite originally was known to insiders as "Force X" and the entire scheme was cloaked in absolute secrecy; to outsiders, the small planning staff was known only as the Special Planning Staff of general headquarters, Far East Command. As the organization grew, due to bureaucratic entanglements, supply orders were rejected because "Force X" was not referenced as a proper organization anywhere in Army manuals. General of the Army Douglas MacArthur (Supreme Commander Allied Powers) asked his chief of staff, Major General Edward Almond, to suggest a new name. Force X's Roman numeral ten reminded Almond of a corps which had fought under MacArthur in the last war—"why not call it the X Corps?" he asked. MacArthur was delighted and approved of the name. General Almond was subsequently chosen by MacArthur as X Corps' new commander.