When the Korean War began in June 1950, the division was deployed to Korea, where it fought in the defense of and the breakout from the Pusan Perimeter in mid-1950, with elements advancing as far as the Yalu River in November. After being thrown back by the Chinese Communist intervention in the war, the division eventually took up positions south of Osan. It participated in a series of United Nations counteroffensives in early 1951, then fought in a stalemate close to the 38th parallel from the middle of the year. The division defended Seoul against Chinese Communist attack from May 1953 to the July armistice, returning to Hawaii in late 1954.