The 2nd Infantry Division (2ID, 2nd ID) ("Indianhead") is a formation of the United States Army. Since the 1960s, its primary mission has been the pre-emptive defense of South Korea in the event of an invasion from North Korea. Approximately 17,000 soldiers serve in the 2nd Infantry Division, with 10,000 stationed in South Korea, accounting for about 35% of the United States Forces Korea personnel. Known as the 2nd Infantry Division-ROK/U.S. Combined Division (2ID/RUCD), the division is bolstered by rotational Brigade Combat Teams (BCTs) from other U.S. Army divisions