From the end of World War II through 1947, the 24th occupied Okinawa, Japan, after which it relocated to Gifu, Japan. On 1 February 1947, the regiment reorganized as a permanent regiment of the 25th Infantry Division. Despite the desegregation of the U.S. armed forces in 1948 by Executive Order 9981, the 24th Infantry remained predominantly African-American, with an officer corps of both African and European Americans. In late June 1950, soon after North Korea invaded South Korea, the 24th deployed to Korea to assist in the Korean War. The 24th Infantry fought throughout the entire Korean peninsula, from the defense of the "Pusan Perimeter" to its breakout and the pursuit of communist forces well into North Korea, to the Chinese counteroffensives, and finally to U.N. counteroffensives that stabilized near the current Demilitarized Zone. The regiment received the Republic of Korea Presidential Unit Citation for its defense of the Pusan Perimeter. The regiment also had two posthumous Medal of Honor recipients, Cornelius H. Charlton and William Thompson. The cases of Lieutenant Leon Gilbert, court martialed for refusing an order from the 24th's commanding officer , and of some other members of the 24th, helped bring greater attention to problems of segregation and discrimination within the U.S. military. The landing at Inchon by U.S. and ROK forces on 15 September finally compelled the North Koreans to withdraw from the Pusan Perimeter. The 24th Infantry was divided into Task Forces Blair and Corley , and they, along with several from other commands, began pursuing the enemy on 27 September.
Question: Which Country compelled the North Koreans to withdraw from the Pusan Perimeter?
Answer: U.S.