20th Marines
| 20th Marine Regiment | |
|---|---|
| Active | June 15, 1943 — August 31, 1944 |
| Country |
 United States of America
|
| Branch |
 United States Marine Corps
|
| Type | Engineer regiment |
| Engagements | |
20th Marine Regiment was an Composite Engineer Regiment of the United States Marine Corps that fought during World War II.
The regiment was a composite of three different types of battalions and a headquarters and service company:
20th Marines was formed on June 15, 1943, at Marine Corps Base Camp Lejeune, North Carolina, it originally consisted of three battalions and was assigned to support the 4th Marine Division. The 1st and 2nd Battalions were made up of the 4th Marine Engineers and Pioneers while the 3rd Battalion was formed with US Navy Construction Battalion personnel also known as Seabees. During the war the Regiment involved in the battle of Roi Namur, Battle of Saipan and Battle of Tinian. On Siapan, the 4th Marine Division assigned 2/20 and 3/20 (4th Pioneers and 121st CB) as the shore party The regiment was inactivated on August 31, 1944 with the 4th Engineer and 4th Pioneer Battalions reassigned to the Division itself. While the 121st NCB remained at Tinian to work on the airfield, the 4th moved on preparing for Iwo Jima. 133 NCB was posted to the slot vacated by the 121st. With the 20th Regiment gone the 133rd was assigned to the 23rd Marines as their shore party and the 4th Pioneers were assigned to the 25th Marines as theirs. The 4th Engineers were then under divisional control. A note concerning the 121st. That Battalion had Marine Officers assigned to it.
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