During October 1949, 1st Battalion, 5th Marines was reactivated in Camp Pendleton, California. During August 1950, the Battalion deployed to fight the Communist force invading the Republic of Korea. Names such as the Pusan Perimeter, Inchon, Seoul and Chosin Reservoir were added to the Battalion's battle vocabulary. At the close of hostilities, the 1st Battalion returned to the United States, settling at Camp Pendleton.