Soon after the war began, General MacArthur had begun planning a landing at Incheon, but the Pentagon opposed him. When authorized, he activated a combined U.S. Army and Marine Corps, and ROK Army force. The X Corps, led by General Edward Almond, Commander, consisted of 40,000 men of the 1st Marine Division, the 7th Infantry Division and around 8,600 ROK Army soldiers. By 15 September, the amphibious assault force faced few KPA defenders at Incheon: military intelligence, psychological warfare, guerrilla reconnaissance, and protracted bombardment facilitated a relatively light battle. However, the bombardment destroyed most of the city of Incheon.

Answer this question, if possible (if impossible, reply "unanswerable"): What Corps included 40,000 men from the 1st Marine Division?
The X Corps