1st Battalion, 23rd Marines

Infantry battalion of the United States Marine Corps

1st Battalion, 23rd Marines (1/23) is one of 32 infantry battalions in the United States Marine Corps, and one of only eight battalions found in the reserve. It is located throughout Texas and Louisiana consisting of approximately 1000 Marines and Sailors. They fall under the command of the 23rd Marine Regiment and the 4th Marine Division.

Provide trained combat and combat support personnel, and units to augment and reinforce the active component in time of war, national emergency, and at other times as national security requires; and have the capability to reconstitute the Division, if required.

The battalion was activated on 20 November 1942, at Marine Corps Base Camp Pendleton, California. They participated in the Battle of Kwajalein (Roi and Namur) where they landed as part of the initial assault on 31 January 1944. Their assault objectives were the heavily defended Japanese occupied twin islands of Roi Namur in the Kwajalein Atoll of the Marshall Islands in the Central Pacific. Roi Namur were two tiny islands in the northern part of the atoll. It was the site of major Japanese three runway airbase. 23rd Marines attacked Roi while the 24th Marines landed on Namur. The regiment secured Roi by the evening. The Battalion's next action came at the Battle of Saipan which began on 15 June 1944. Their transport there was APA 35 the USS Calloway. Saipan was the linchpin in the Japanese defense of the Central Pacific. To make an amphibious assault even more difficult, it had several towns and a civilian population of about 20,000. Using the lessons learned at Roi Namur, intensive pre invasion naval bombardments and air strikes on Japanese positions began on 11 June 1944. Marines came ashore and were immediately met with intense and accurate fire from Japanese mortars, howitzers and antiboat guns. By 17 June 1944 a beachhead had been secured and on 18 June the Marines captured Aslito Airfield cutting Japanese defenses in two. The forces had to fight back a fierce Japanese counterattack in the form of banzai charges. For Siapan the 23rd landed on beaches blue 1 & 2. Shore party for 1/23 was the third battalion 20th Marines which was the 121st Seabees. The 4th Marine Division completed mopping up on Saipan on 16 July 1944 leaving only a week for preparation for the invasion of Tinian. The Invasion of Tinian commenced on 25 July 1944. The 4th Marine Division was selected to lead the assault on Tinian. Again, the pre invasion bombardment built to a crescendo as H hour approached. Assault elements met only limited small arms fire when they reached the beach. With nightfall, came the expected Japanese counterattacks. The division employed flame throwers, demolition charges and automatic weapons fire to route Japanese soldiers out of caves, bunkers, and other defensive positions on the southern portion of the island. One of the most difficult aspects of the final phase of battle was convincing Japanese soldiers and thousands of civilians to surrender. The final combat action for 1/23 would come during the Battle of Iwo Jima. Iwo Jima was only 750 miles from Tokyo and was a major objective on the way to the Japanese mainland. The Japanese were painfully aware of the strategic importance of Iwo Jima and had prepared extensive and formidable defenses with a network of miles of caves and tunnels. The tunnels were in the islands black volcanic rocky base well protected from preinvasion naval and air bombardment. The 4th Marine Division landed in the first assault wave on 19 February 1945 The 23rd and 24th Marine Regiments led the division's assault with 1/23 being the left Assault Battalion on yellow beach 1. They landed from APA 158 the USS Newberry. The 23rd Marines were ordered to seize the Motoyama Airfield #1 for the 133rd Seabees to get operational. High seas, heavy surf and loose volcanic soil made movement off the beaches difficult. By 20 February 1945, 23rd Marines had made good progress towards capturing the airfield. With the exception of a few remaining small pockets of resistance, the division had defeated the resolute and entrenched enemy in its zone of action in twenty days at a cost of nearly 50 percent combat efficiency. The 23rd did not have a Pioneer Battalion for the assault so the Seabees of the 133rd Naval Construction Battalion were attached to the 23rd and assigned that job. A Co. 133 was Shore Party to 1/23 until relieved on D plus 18 by the Army Garrison Shore Party.

The battalion was mobilized for the first time since World War II in January 1991 in support of Operation Desert Shield. The unit was deployed to Marine Corps Base Camp Pendleton, California, in support of the 1st Marine Division during this time.