3rd Battalion, 23rd Marine Regiment (3/23) is a reserve infantry battalion in the United States Marine Corps located throughout the Southern United States consisting of approximately 800 Marines and Sailors. The battalion was first formed in 1943 for service in the Pacific Theater of Operations during World War II, taking part in a number of significant battles including those at Saipan and Iwo Jima before being deactivated at the end of the war. In the early 1960s, the unit was reactivated as a reserve battalion. The battalion is headquartered in Saint Louis, Missouri, with outlying units throughout the Southern United States. 3/23 falls under the command of the 23rd Marine Regiment and the 4th Marine Division. Recent operations have included tours in Iraq and Afghanistan.