United States Marine Corps

===Historical mission===
The Marine Corps was founded to serve as an infantry unit aboard naval vessels and was responsible for the security of the ship and its crew by conducting offensive and defensive combat during [[Naval boarding|boarding actions]] and defending the ship's officers from [[mutiny]]; to the latter end, their quarters on the ship were often strategically positioned between the officers' quarters and the rest of the vessel. Continental Marines manned raiding parties, both at sea and ashore. America's first amphibious assault landing occurred early in the [[American Revolutionary War|Revolutionary War]] on 3 March 1776 as the Marines gained control of [[Fort Montagu]] and [[Old Fort of Nassau|Fort Nassau]], a [[British Empire|British]] ammunition depot and naval port in [[New Providence]], the Bahamas. The role of the Marine Corps has expanded significantly since then; as the importance of its original naval mission declined with changing naval warfare doctrine and the professionalization of the naval service, the Corps adapted by focusing on formerly secondary missions ashore. The Advanced Base Doctrine of the early 20th century codified their combat duties ashore, outlining the use of Marines in the seizure of bases and other duties on land to support naval campaigns. In 1987 the USMC Sea School was closed; in 1998 all Marine Detachments on board ships were disbanded. 

Throughout the late 19th and 20th centuries, Marine detachments served aboard Navy cruisers, battleships, and aircraft carriers. Marine detachments served in their traditional duties as a ship's landing force, manning the ship's weapons and providing shipboard security. Marine detachments were augmented by members of the ship's company for landing parties, such as in the [[First Sumatran expedition]] of 1832 and continuing in the Caribbean and [[United States occupation of Veracruz|Mexican campaign]]s of the early 20th centuries. Marines developed tactics and techniques of amphibious assault on defended coastlines in time for use in World War II.<ref name="Lawliss">{{Cite book |last= Lawliss |first= Chuck |title= The Marine Book: A Portrait of America's Military Elite |publisher= Thames and Hudson |year= 1988 |location= New York}}</ref> During World War II, Marines continued to serve on capital ships, and some were assigned to man anti-aircraft batteries.<ref>{{Cite book |last=Hough, LtCol. |first=Frank O. |url=https://www.usmcu.edu/Portals/218/History%20of%20the%20U.S.%20Marine%20Corps%20in%20WWII%20Vol%20I%20-%20Pearl%20Harbor%20to%20Guadacanal%20%20PCN%2019000262400.pdf |title=Pearl Harbor to Guadalcanal: History of U.S. Marine Corps Operations in World War II |last2=Ludwig |first2=Verle E. |last3=Shaw, Jr. |first3=Henry I. |publisher=Historical Branch, G-3 Division, Headquarters, U.S. Marine Corps |year=1989 |volume=1 |language=en |lccn=58-60002 |archive-url=https://archive.org/details/historyofusmarin01usma/page/n3/mode/2up |archive-date=2013-06-25}}</ref>

In 1950,<ref>{{Cite web|url=https://www.marines.mil/Portals/1/Publications/A%20Chronology%20of%20the%20United%20States%20Marine%20Corps%201947-1964%20%20PCN%2019000318200.pdf|title=A Chronology of the United States Marine Corps Historical Reference Pamphlet|date=1947–1964|website=Marines.mil|access-date=29 April 2020|archive-date=5 June 2020|archive-url=https://web.archive.org/web/20200605151639/https://www.marines.mil/Portals/1/Publications/A%20Chronology%20of%20the%20United%20States%20Marine%20Corps%201947-1964%20%20PCN%2019000318200.pdf|url-status=live}}</ref> President [[Harry S. Truman|Harry Truman]] responded to a message from U.S. Representative [[Gordon L. McDonough]]. McDonough had urged President Truman to add Marine representation on the [[Joint Chiefs of Staff]]. President Truman, writing in a letter addressed to McDonough, stated that "The Marine Corps is the Navy's police force and as long as I am President that is what it will remain. They have a propaganda machine that is almost equal to [[Joseph Stalin|Stalin's]]." McDonough then inserted [https://commons.m.wikimedia.org/wiki/File:Letter,_Harry_Truman_to_Gordon_McDonough,_29_August_1950_(15310975758).jpg President Truman's letter], dated 29 August 1950, into the ''[[Congressional Record]]''. Congressmen and Marine organizations reacted, calling President Truman's remarks an insult and demanded an apology. Truman apologized to the Marine commandant at the time, writing, "I sincerely regret the unfortunate choice of language which I used in my letter of August 29 to Congressman McDonough concerning the Marine Corps." While Truman had apologized for his metaphor, he did not alter his position that the Marine Corps should continue to report to the Navy secretary. He made amends only by making a surprise visit to the [[Marine Corps League]] a few days later, when he reiterated, "When I make a mistake, I try to correct it. I try to make as few as possible." He received a standing ovation.<ref>{{Cite news|last=Battistella|first=Edwin|url=https://www.politico.com/magazine/story/2014/05/the-art-of-the-political-apology-106458/|title=The Art of the Political Apology|date=7 May 2014|work=Politico.com|access-date=14 January 2024|archive-date=20 October 2020|archive-url=https://web.archive.org/web/20201020070506/https://www.politico.com/magazine/story/2014/05/the-art-of-the-political-apology-106458_Page2.html|url-status=live}}</ref>

When gun cruisers were retired by the end of the 1970s, the remaining Marine detachments were only seen on battleships and carriers. Its original mission of providing shipboard security ended in the 1990s.<ref>{{Cite web |title=The Corps' Salty Seadogs Have All But Come Ashore: Seagoing Traditions Founder as New Millennium Approaches |url=http://public2.nhhcaws.local/research/library/online-reading-room/title-list-alphabetically/c/the-corps-salty-seadogs-have-all-but-come-ashore-seagoing-traditions-founder-as-new-millennium-approaches.html |access-date=2023-12-16 |website=public2.nhhcaws.local |language=en-US}}</ref>