The United States Marine Corps serves as an expeditionary force-in-readiness. As outlined in 10 U.S.C. § 5063 and as originally introduced under the National Security Act of 1947, it has three primary areas of responsibility:
- The seizure or defense of advanced naval bases and other land operations to support naval campaigns;
- The development of tactics, technique, and equipment used by amphibious landing forces in coordination with the Army and Air Force; and
- Such other duties as the President may direct.
This last clause, while seemingly redundant given the President's position as Commander-in-chief, is a codification of the expeditionary duties of the Marine Corps. It derives from similar language in the Congressional acts "For the Better Organization of the Marine Corps" of 1834, and "Establishing and Organizing a Marine Corps" of 1798. In 1951, the House of Representatives' Armed Services Committee called the clause "one of the most important statutory — and traditional — functions of the Marine Corps." It noted that the corps has more often than not performed actions of a non-naval nature, including its famous actions in Tripoli, the War of 1812, Chapultepec, and numerous counter-insurgency and occupational duties (such as those in Central America), World War I, and the Korean War. While these actions are not accurately described as support of naval campaigns nor as amphibious warfare, their common thread is that they are of an expeditionary nature, using the mobility of the Navy to provide timely intervention in foreign affairs on behalf of American interests.
In addition to its primary duties, the Marine Corps has missions in direct support of the White House and the State Department. The Marine Band, dubbed the "President's Own" by Thomas Jefferson, provides music for state functions at the White House. Marines guard presidential retreats, including Camp David, and the Marines of the Executive Flight Detachment of HMX-1 provide helicopter transport to the President and Vice President, using the call signs "Marine One" and "Marine Two" respectively. By authority of the 1946 Foreign Service Act, the Marine Security Guards of the Marine Embassy Security Command provide security for American embassies, legations, and consulates at more than 140 posts worldwide.
As in any military organization, the official and unofficial traditions of the Marine Corps serve to reinforce camaraderie and set the service apart from others. The Corps' embrace of its rich culture and history is cited as a reason for its high esprit de corps.
- The Marines' Hymn dates back to the 19th century and is the oldest official song in the United States armed forces.
- The Marine motto Semper Fidelis means always faithful in Latin, often appearing as Semper Fi; also the name of the official march of the Corps, composed by John Phillip Sousa. The mottos "Fortitudine" (With Fortitude); By Sea and by Land, a translation of the Royal Marines' Per Mare, Per Terram; and To the Shores of Tripoli were used until 1868.
- The Marine Corps emblem is the Eagle, Globe, and Anchor, sometimes abbreviated "EGA", adopted in 1868.
- The Marine Corps seal includes the emblem, also is found on the flag of the United States Marine Corps, and establishes scarlet and gold as the official colors.
- Two styles of swords are worn by Marines: the officers' Mameluke Sword, similar to the Persian shamshir presented to Lt. Presley O'Bannon after the Battle of Derna, and the Marine NCO sword.
- The Marine Corps Birthday is celebrated every year on 10 November in a cake-cutting ceremony where the first slice of cake is given to the oldest Marine present, who in turn hands it off to the youngest Marine present. The celebration includes a reading of Marine Corps Order 47, Commandant Lejeune's Birthday Message.
- Close Order Drill is heavily emphasized early on in a Marine's initial training, incorporated into most formal events, and is used to teach discipline by instilling habits of precision and automatic response to orders, increase the confidence of junior officers and noncommissioned officers through the exercise of command and give Marines an opportunity to handle individual weapons.
- An important part of the Marine Corps culture is the traditional seafaring naval terminology derived from its history with the Navy.
- Devil Dog: The term "Devil Dog" has its origins at Belleau Wood. It was in a dispatch from the German front lines to their higher headquarters explaining the current battle conditions that described the fighting abilities of the new, fresh Americans as fighting like "Teufel Hunden" or "Hounds from Hell.
- Leatherneck: Tthe term "Leatherneck" was derived from a leather stock once worn around the neck by both American and British Marines; used as a fashion to help military bearing by keeping the chin up and also by protecting the neck from sword blows.
- Jarhead: The term Jarhead was derived from the regulation "high and tight" haircut.
Adapt and Overcome.
I am humbled and honored by my service in the Marine Corps. Today I celebrate with the few, the proud. Happy Birthday, Marines!