During October 1949, 3rd Battalion, 5th Marines, was reactivated on Guam. During August 1950, the Battalion deployed to fight against the North Korean army invading the Republic of Korea (South Korea) during the Korean War. The 3rd Battalion fought at such places as the Pusan Perimeter, Inchon, Seoul and Chosin Reservoir. It inflicted heavy casualties on Chinese forces at the Battle of Hwacheon. At the close of hostilities, the 3rd Battalion returned to the United States, settling at MCB Camp Pendleton. The battalion's nickname "Darkhorse" sprang from the radio call sign of its commander in Korea, Colonel Robert Taplett, who was known as "Darkhorse Six".