How the U.S. Marines Work

Marines logo
Photo courtesy of the The U.S. Marines
The U.S. Marine Corps logo
Of the four branches of the U.S. military that fall within the Department of Defense (Army, Navy, Air Force, Marines), the United States Marine Corps is by far the smallest. Yet the Marines have taken on some of the toughest missions military planners can throw at them, and have developed a unique military culture that thrives on challenge and hardship. In fact, all Marines proudly declare that there are no “former” or “ex” Marines – a Marine stays a Marine for life.

In this article we'll look at why there is a Marine Corps, how it's structured, the history behind the Corps, how to join, life inside, and leaving.

Marine Corps Purpose
The modern Marine Corps is focused on “force projection;” specifically, the projection of U.S. military power from Navy ships onto hostile landing areas. Marines have spearheaded amphibious assaults and gained footholds for American troops throughout U.S. history. They secure or set up advance bases from which the Army and Air Force can operate. In addition, the Marines can be used for “other duties as the President may direct,” according to the 1834 Marine Corps Law. The Marines operate in a state of readiness for combat unmatched by units in other military branches. A Marine unit has everything it needs to leap right into combat, including logistical support and close air support. Plus, the Marines keep units stationed on Navy ships that are “on float” around the world. That puts them closer to potential trouble spots than troops stationed in the United States

Amphibious assault ship
Photo courtesy of the U.S. Marines/Photographer Lance Cpl. Lucian Friel
An amphibious assault vehicle during ship operation training.

The Marines and the Navy
Although the Marine Corps is separate from the Navy, the two forces both operate under the Department of the Navy and have a close relationship. Marine forces often provide security on Navy ships, and many Navy ships have Marine units stationed on them (including an air wing) on a semi-permanent basis. Certain “behind the scenes” jobs, such as chaplains or medics, are filled in the Marine Corps ranks by Navy personnel because the Marines don’t train those positions. These personnel wear Marine uniforms with Navy insignias. Marine officers are trained at the Naval Academy, and Navy officer training includes some training by a Marine Corps drill instructor.

The “as the President may direct” portion of the Marine Corps’ job description puts them in quite a few non-amphibious situations, including combat far from beaches, running security detail on some Navy ships (originally the Corps’ primary function), protecting U.S. embassies as well as the White House, and transporting the president and vice president in Marine helicopters.


Marine Corps Structure

Commandant of the Marines
Photo courtesy of the U.S. Marines
Commandant of the Marine Corps, General James T. Conway
Although the Marine Corps is a separate branch of the U.S. military, it does not have its own department within the Department of Defense as the Army, Navy and Air Force do. The Marine Corps is part of the Department of the Navy. At an administrative, political and civilian level, the Marines operate beneath the Secretary of the Navy. However, the highest ranking Marine Corps officer, the Commandant of the Marine Corps, does not answer to any other military officer. He is the military head of the Corps. Every Marine Corps Commandant has lived in the Marine Barracks in Washington, D.C. It is the oldest official building in Washington that has remained in continuous use for its original purpose. [Source: Global Security]. The Marines pride themselves on efficiency, claiming to supply 20 percent of the U.S. armed forces’ combat power while using only 6.5 percent of the Department of Defense’s budget. [Source: Marines Magazine].

The Marines are divided into four separate groups:

  • Operating Forces – Do the actual fighting.
  • Headquarters Marine Corps (HQMC) – Upper echelons of Marine Corps leadership, based in Arlington, VA.
  • Supporting Establishment – Provides logistical support to Corps missions. This includes supplying ammo and food, medical facilities and communications equipment.
  • Marine Forces Reserve – Train one weekend per month and two weeks per year and can be called up when needed to support or replace Marines; ready reserves are Marines who have completed their active duty but may be recalled if needed.

Urban warfare training
Photo courtesy of the U.S. Marines/Photographer: Sgt. Jerad W. Alexander
Marines advance on a building during urban warfare training.
The Operating Forces are split between Marine Forces Pacific and Marine Forces Atlantic, with each force in charge of operations in their respective area. While the Corps is divided into Divisions, Regiments and Battalions, it is more meaningful to recognize that Marines are organized into Expeditionary Forces, Brigades and Units when they are sent to deal with a specific problem. The deployment of Marine units is not limited by a rigid organizational structure, allowing for each Expeditionary group to be tailored to a specific mission profile. For example, a mission in a heavily populated area will require troops suited for urban warfare, while missions into mountainous regions will not require many tanks. An Expeditionary group of any size brings everything it needs to get the job done, including the ground combat element (GCE) and an air combat element (ACE) for close air support and helicopter insertion. They will also have enough supplies for a minimum of two weeks – most have 60 days of supplies. This reflects a revision of doctrine after a debacle at Guadalcanal in World War II. Navy vessels dropped the Marines on the beach, but were driven back by Japanese fire before they could unload equipment and supplies. The Marines were forced to fight and survive using captured weapons and rice (Halberstadt, 21).

Storage unit
Photo courtesy of the U.S. Marines/Photographer: Lance Cpl. Brandon L. Roach
Lance Cpl. Jonathan W. Chaline tidies one of his storage units where supplies are stored at Al Asad, Iraq.
This combined arms strategy is central to the Marine Corps. While the other armed forces have to form a “unified command” to combine Air Force, Army and Navy operations, the Marines bring everything they need with them to get the mission done. While the Army has light infantry units capable of deploying more quickly than the Marines, they require reinforcement and resupply within a few days. A Marine Expeditionary Unit can arrive relatively quickly (obviously not as quickly as light infantry paratroopers) with all the armor, air support and supplies they need for an extended mission.

The Corps also places a heavy emphasis on decentralization of command. Junior officers are given greater responsibility and decision-making abilities than soldiers of the same rank in other armed forces. The general rule is: “Follow the spirit of an order (from higher ranking officers), even if you don’t follow the order to the letter.” In other words, if a Marine unit is ordered to get something done, the individual commander within that unit has the freedom to decide the best way to do it.

Marines vs. the Army
The Marine Corps has a long-standing rivalry with the U.S. Army. The Marines’ elitist attitude often grates on Army troops, who feel that the Marines duplicate the Army’s capabilities. The Marines, for their part, feel that they do a better job at their specific tasks and are crucial to U.S. military goals. In the wake of both World War II and the Vietnam War, there was a strong push in the Department of Defense to get rid of the Marines altogether and fold their capabilities entirely into the Army. However, there are quite a few retired Marines who have gone on to political careers. Their efforts to preserve the Marines as a force and as a tradition have made it unlikely that the Marine Corps will be disbanded in the near future.

Marine Corps Ranks and Abbreviations
Commissioned Officers Warrant Officers Enlisted
General (GEN) Commandant of the Marine Corps Chief Warrant Officer 5 (CWO5) Sergeant Major of the Marine Corps (SgtMajMC)
Lieutenant General (Lt. Gen) Chief Warrant Officer 4 (CWO4) Master Gunnery Sergeant (MGySgt)
Major General (Maj. Gen.) Chief Warrant Officer 3 (CWO3) Sergeant Major (SgtMaj)
Brigadier General (Brig. Gen) Chief Warrant Officer 2 (CWO2) First Sergeant (1st SG)
Colonel (COL) Warrant Officer 1 (WO) Master Sergeant (MSG)
Lieutenant Colonel - (Lt. Col.)   Gunnery Sergeant (GySgt)
Major (MAJ)   Staff Sergeant (Ssgt)
Captain (CPT)   Sergeant (Sgt)
First Lieutenant (1st LT)   Corporal (CPL)
Second Lieutenant (2nd LT)   Lance Corporal (LCpl)
    Private First Class (PFC)
    Private (PV)


Marine Corps History and Joining Up

First Commondant of the Marines
Photo courtesy of the U.S. Marines
Samuel Nicholas, first Commandant of the U.S. Marine Corps.
Officially, the history of the U.S. Marines began on November 10, 1775, when the Continental Congress authorized the formation of the Continental Marines for use in the war against England. The first troops were recruited at a tavern in Philadelphia. At the end of the Revolutionary War, the Marines (who were not a very prestigious organization at the time) were disbanded.

In 1798, the Marine Corps was reestablished to help combat pirates of the Barbary Coast who were attacking U.S. merchant ships in the Mediterranean region. In those early years, the Marines acted as “naval infantry,” working aboard Navy ships and going ashore or onto enemy ships to fight when necessary. They also served as a security and police force on Navy ships. At the time, many Navy sailors were non-professionals who had been conscripted into service. The possibility of mutiny was very real. The Marines on board were often positioned in between the crew quarters and the officers. While at sea, the Marines were under the command of the Navy. When they went ashore, they were under Army command.

pirate book
Photo courtesy of Amazon
The Pirate Coast, a book about the first Marines and the pirates they fought.

The pirate issue came to a head when the African nation of Tripoli declared war on the United States in 1801. A handful of Marines with a large group of mercenaries marched overland to the city of Derna and captured it after several hours of hard fighting. The incident was immortalized in the Marines’ Hymn.

Iwo Jima
Photo courtesy of the U.S. Marines/Photographer: Joe Rosenthal
Five Marines and a Navy corpsman raise the second American flag on top of Mount Suribachi on February 23, 1945.

Marines have seen action to some extent in every U.S. war. They saw heavy fighting in World War I, but it was in World War II that they endured some of the toughest battles ever fought by American soldiers. The Pacific Theater of the war required the conquering of dozens of small islands, airfields and bases that were held by entrenched Japanese forces. Island by island, the Marines ground out costly victories, losing thousands of men for each tiny atoll they took. It was here that they perfected the art of the amphibious assault. On a small island called Iwo Jima, the Marines’ victory was frozen in time by a famous photograph showing Marines struggling to raise an American flag. They eventually took the Philippines and landed in Japan and China to accept the surrender of Japanese soldiers. Almost 20,000 Marines died during the course of the war (Lawliss, 57).

The Marines were no less valuable (and bloodied) in Korea and Vietnam, and spearheaded several major assaults through Iraqi lines during Operation Desert Storm. [Source: The Marines]. During the Iraq War, Marines were in the thick of daily battles with insurgents in Fallujah, Samarra and Sadr City, and are responsible for patrolling and peacekeeping in that region. [Source: The Washington Post].

Photo courtesy of the U.S. Marines/Department of Defense
Marines exit their transportation to begin a search and destroy operation in Vietnam, November 18, 1967.

In the future, the Marines plan to constantly examine and adjust their doctrine to improve their ability to deal with modern warfare. In the age of IEDs and roadside bombs, Marines are looking toward cultural training, decentralized decision-making and special anti-terrorism units to combat 21st century warfare tactics [Source: Marines Magazine].

Joining the Marines
Those who wish to become an officer in the Marines can apply for Officer Candidates School, which offers a grueling training regimen and an officer’s commission upon graduation. Potential Marine Corps officers can also attend the Naval Academy, a four-year undergraduate institution with a very rigorous physical and academic program. A Congressional nomination is required to apply.

Officer Candidate School
Photo courtesy of the U.S. Department of Defense
Officer Candidate School students turn toward the source of a simulated grenade explosion.

Most Marines, however, begin their military career in Marine Corps boot camp at Parris Island, South Carolina or at the Marine Corps Recruit Depot in San Diego, California. The 12-week training program is, by all accounts, more difficult than most armed services in the United States or elsewhere. Recruits are united by their loathing (and later respect) for a hard-nosed and leather-lunged Drill Instructor, who will literally drill Marine Corps values and skills into them. The Marine Corps training matrix provides a detailed look at Marine boot camp. All Marines are extensively trained in marksmanship – another part of Marine doctrine states that every Marine is a rifleman, from the front lines to the cooks and clerks.

Fitness test
Photo courtesy of the U.S. Marines/Photographer: Lance Cpl. Dorian Gardner
Pvt. Nicholas L. Warner does pull-ups during the first event of the final physical fitness test.
Recruits should be aware that they will be asked to run 1.5 miles in less than 13 minutes and 30 seconds, do two full pull-ups and 44 crunches shortly after they arrive (female recruits must run the 1.5 miles in less than 15 minutes, do a 12-second flexed-arm hang, and also do 44 crunches). Failure will result in time spent in remedial courses designed to whip the recruits into decent physical condition. In other words, put in some time at the gym before you get on the bus for Parris Island.

Following graduation, Marines get a ten-day leave and then attend additional training in a specific area or career track. There are restrictions and prerequisites for many career tracks and specialties, so not every Marine gets to choose exactly what he or she wants to do. They will then be assigned to a base or airfield. The Marine’s preference for deployment is noted, but the priority for base assignment is where the Corps needs you, not where you’d like to live.


Life in the Marines

Marines may be stationed at any of about 20 bases, camps and airfields throughout the United States (with several bases also located overseas). A housing stipend provides living quarters for Marines and sometimes their families, usually on-base. The newest Marines live in barracks similar to a college dormitory. Like other U.S. military bases, Marine Corps bases offer essentials (shopping, church, school, medical facilities) and a variety of recreational activities (sports teams, movie theaters, seminars, restaurants, bowling, et cetera).

Photo courtesy of the U.S. Marines/Photographer: Pfc. Christopher D. Lyttle
Pfc. David V. Telles and Pfc. Jack E. Severson do a general cleanup of their barracks room.

Many Marines will spend portions of their active duty stationed aboard Navy vessels. For them, time on a Navy deployment (lasting roughly six months) is much the same as it is for the sailors themselves – cramped, busy and at times rather boring. Marines remain under the command of their officers while on board, but everyone on a Navy vessel is under the command of the ship’s captain.

Rails of a ship
Photo courtesy of the U.S. Marines/Photographer: Cpl. Eric R. Martin
Marines and Sailors man the rails of the ship while pulling into a port in Palma, Spain.

During wartime, Marines experience an interesting range of hardships. The Iraq War offers the constant fear of roadside or suicide bombings and the uncertainty as to whether any given Iraqi citizen is an innocent civilian or an insurgent. They are far from home, facing death on a daily basis and watching their close friends get killed or wounded – in other words, life for a Marine hasn’t changed much in 200 years.

Leaving the Marines
As members of a U.S. military organization, all Marine Corps personnel are subject to the Uniform Code of Military Justice. Dismissal from the Marines can take a variety of forms, from an honorable discharge to a court martial, depending on the circumstances surrounding the dismissal. See How the Army Works for a full explanation.

Photo courtesy of the U.S. Marines/Photographer: Lance Cpl. George J. Papastrat
Veterans from the San Diego area raise their hand in salute during the National Anthem during a Veterans Day celebration.

Marine Corps veterans and retirees are eligible for a host of benefits ranging from burial in state cemeteries, health and life insurance, low-interest loans for mortgages or small businesses, and veterans’ health care. The full suite of benefits available may depend on the nature of the veteran’s dismissal – usually an honorable discharge or retirement is necessary for access to all benefits. A search for answers to specific questions about veterans’ benefits begins here: The National Archives.

For lots more information on the Marine Corps and related topics, check out the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links


  • Fainaru, Steve. “For Marines, a Frustrating Fight: Some in Iraq Question How and Why War Is Being Waged.” Washington Post, Oct. 10, 2004.
  • Fisher, Cindy. “CMC: 'Changes in Corps' future will benefit marines' end-strength, restructure to increase crucial capabilities: big changes are on the horizon for the Marine Corps.” Marines Magazine, April-June 2005.
  • “Marine Corps Organization.”
  • Halberstadt, Hans. U.S. Marine Corps. Zenith Press (December 17, 1993). 978-0879387693.
  • Lawliss, Chuck. The Marine Book: A Portrait of America's Military Elite. Thames & Hudson; Rev Sub edition (June 1992). 978-0500276655.
  • “Historical Timeline.”
  • Time Magazine. “The Next Marine Battle.” March 30, 1970.,9171,942207-1,00.html