Marine Detachment aboard USS Augusta in the 1930s
Marine Detachment aboard USS Augusta in the 1930s

Marine Detachment or MarDet was a unit of 35 to 85 United States Marines aboard large warships including cruisers, battleships, and aircraft carriers. They were a regular component of a ship's company from the formation of the United States Marine Corps until the 1990s.[1] Missions of the Marine Detachment evolved, and included protecting the ship's captain, security and defense of the ship, operating the brig, limited action ashore, securing nuclear weapons and ceremonial details.


Marines served aboard sailing ships as a small amphibious force able to capture and hold minor port facilities as required for protection of American interests. Marine sharpshooters were often stationed in the rigging during ship-to-ship combat to fire at officers and helmsmen aboard enemy warships. Marines often operated naval artillery during general quarters when the distances of gunnery engagements exceeded the range of small arms.[2]


Each MarDet included a Marine Corps commanding officer who reported to the Commandant of the Marine Corps through the ship's captain. When more than one Marine officer was assigned to a ship, United States Navy Regulations required one Marine officer to be aboard ship at all times unless excused by the ship's captain. Marine officers below the rank of major sometimes served as officer of the deck.[2]

Horse Marines

The Marines also employed mounted Horse Detachments called "Horse Marines" in places such as Peking, China from early 1900 to 1938 and Nicaragua in 1927 during the Second Nicaraguan Campaign.[3] In Africa during the First Barbary War 1805-05 and in the diplomatic mission to Abyssinia in 1903, the Marine Detachments used camels.[3]


  1. ^ Richardson, Herb and Keene, R. R. "The Corps' Salty Seadogs Have All But Come Ashore: Seagoing Traditions Founder as New Millennium Approaches", Naval History and Heritage Command website, September 5, 2017. Retrieved October 15, 2021.
  2. ^ a b Mayo, Claude Banks (1939). Your Navy. Los Angeles: Parker & Baird Company. pp. 311–317.
  3. ^ a b Macomber, Frank. "Horse Marines...Rich in History", Sunday The Indianapolis Star Magazine, volume 64, number 126, October 9, 1966, pages 30 and 32. (subscription required)