10 November 1775
(248 years, 11 months)
(as the Continental Marines)

---

Country United StatesTypeMaritime land forceRoleSizePart ofUnited States Armed Forces
Department of the NavyHeadquartersThe Pentagon
Arlington County, Virginia, U.S.Nickname(s)"Jarheads", "Devil Dogs", "Teufel Hunden", "Leathernecks"Motto(s)Semper fidelis ("Always faithful")ColorsScarlet and gold
   March"Semper Fidelis" PlayMascot(s)English bulldogAnniversaries10 NovemberEquipmentList of U.S. Marine Corps equipmentEngagementsDecorations

Presidential Unit Citation

Joint Meritorious Unit Award
Navy Unit Commendation
Valorous Unit Award

Meritorious Unit Commendation
French Croix de guerre 1914–1918
Philippine Presidential Unit Citation
Korean Presidential Unit Citation
Vietnam Gallantry Cross

Vietnam Civil Actions MedalWebsiteCommandersCommander-in-Chief President Joe BidenSecretary of Defense Lloyd AustinSecretary of the Navy Carlos Del ToroCommandant Gen Eric M. SmithAssistant Commandant Gen Christopher J. MahoneySergeant Major of the Marine Corps SMMC Carlos A. RuizInsigniaFlagSealEmblem ("Eagle, Globe, and Anchor" or "EGA")WordmarkSong"The Marine's Hymn" Play

United States Armed Forces
Executive departments
Department of Defense Department of Homeland Security
Staff
Office of the Secretary of Defense Joint Chiefs of Staff
Military departments
Department of the Army Department of the Navy Department of the Air Force
Military services
United States Army United States Marine Corps United States Navy United States Air Force United States Space Force United States Coast Guard
Command structure
Unified combatant commands Africa Command Central Command European Command Indo-Pacific Command Northern Command Southern Command Cyber Command Space Command Special Operations Command Strategic Command Transportation Command
Combat support agencies Defense Contract Management Agency Defense Health Agency Defense Information Systems Agency Defense Intelligence Agency Defense Logistics Agency Defense Threat Reduction Agency National Geospatial-Intelligence Agency National Security Agency Central Security Service
v t e

The United States Marine Corps (USMC), also referred to as the United States Marines, is the maritime land force service branch of the United States Armed Forces responsible for conducting expeditionary and amphibious operations through combined arms, implementing its own infantry, artillery, aerial, and special operations forces. The U.S. Marine Corps is one of the eight uniformed services of the United States.

The Marine Corps has been part of the United States Department of the Navy since 30 June 1834 with its sister service, the United States Navy. The USMC operates installations on land and aboard sea-going amphibious warfare ships around the world. Additionally, several of the Marines' tactical aviation squadrons, primarily Marine Fighter Attack squadrons, are also embedded in Navy carrier air wings and operate from the aircraft carriers.

The history of the Marine Corps began when two battalions of Continental Marines were formed on 10 November 1775 in Philadelphia as a service branch of infantry troops capable of fighting both at sea and on shore. In the Pacific theater of World War II, the Corps took the lead in a massive campaign of amphibious warfare, advancing from island to island. As of 2022, the USMC has around 177,200 active duty members and some 32,400 personnel in reserve.

As outlined in 10 U.S.C. § 5063 and as originally introduced under the National Security Act of 1947, three primary areas of responsibility for the U.S. Marine Corps are:

• Seizure or defense of advanced naval bases and other land operations to support naval campaigns;
• 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 or Department of Defense may direct.

This last clause 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 counterinsurgency 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.

The Marine Band, dubbed the "President's Own" by John Adams, provides music for state functions at the White House. Marines from Ceremonial Companies A & B, quartered in Marine Barracks, Washington, D.C., 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, with the radio call signs "Marine One" and "Marine Two", respectively. The Executive Flight Detachment also provides helicopter transport to Cabinet members and other VIPs. 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.

The relationship between the Department of State and the U.S. Marine Corps is nearly as old as the Corps itself. For over 200 years, Marines have served at the request of various Secretaries of State. After World War II, an alert, disciplined force was needed to protect American embassies, consulates, and legations throughout the world. In 1947, a proposal was made that the Department of Defense furnish Marine Corps personnel for Foreign Service guard duty under the provisions of the Foreign Service Act of 1946. A formal Memorandum of Agreement was signed between the Department of State and the Secretary of the Navy on 15 December 1948, and 83 Marines were deployed to overseas missions. During the first year of the program, 36 detachments were deployed worldwide.

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 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 Revolutionary War, on 3 March 1776, as the Marines gained control of Fort Montagu and Fort Nassau, a 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 Mexican campaigns of the early 20th centuries. Marines developed tactics and techniques of amphibious assault on defended coastlines in time for use in World War II. During World War II, Marines continued to serve on capital ships, and some were assigned to man anti-aircraft batteries.

In 1950, President 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, "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 Stalin's." McDonough then inserted 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.

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.

The Marine Corps fulfills a critical military role as an amphibious warfare force. It is capable of asymmetric warfare with conventional, irregular, and hybrid forces. While the Marine Corps does not employ any unique capabilities, as a force, it can rapidly deploy a combined-arms task force to almost anywhere in the world within days. The basic structure for all deployed units is a Marine Air-Ground Task Force (MAGTF) that integrates a ground combat element, an aviation combat element, and a logistics combat element under a common command element. While the creation of joint commands under the Goldwater–Nichols Act has improved interservice coordination between each branch, the Corps's ability to permanently maintain integrated multielement task forces under a single command provides a smoother implementation of combined-arms warfare principles.

The close integration of disparate Marine units stems from an organizational culture centered on the infantry. Every other Marine capability exists to support the infantry. Unlike some Western militaries, the Corps remained conservative against theories proclaiming the ability of new weapons to win wars independently. For example, Marine aviation has always been focused on close air support and has remained largely uninfluenced by air power theories proclaiming that strategic bombing can single-handedly win wars.

This focus on the infantry is matched with the doctrine of "Every Marine [is] a rifleman", a precept of Commandant Alfred M. Gray, Jr., emphasizing the infantry combat abilities of every Marine. All Marines, regardless of military specialization, receive training as a rifleman, and all officers receive additional training as infantry platoon commanders. During World War II at the Battle of Wake Island, when all the Marine aircraft were destroyed, pilots continued the fight as ground officers, leading supply clerks and cooks in a final defensive effort. Flexibility of execution is implemented via an emphasis on "commander's intent" as a guiding principle for carrying out orders, specifying the end state but leaving open the method of execution.

The amphibious assault techniques developed for World War II evolved, with the addition of air assault and maneuver warfare doctrine, into the current "Operational Maneuver from the Sea" doctrine of power projection from the seas. The Marines are credited with developing helicopter insertion doctrine and were the earliest in the American military to widely adopt maneuver-warfare principles, which emphasize low-level initiative and flexible execution. In light of recent warfare that has strayed from the Corps's traditional missions, the Marines have renewed an emphasis on amphibious capabilities.

The Marine Corps relies on the Navy for sealift to provide its rapid deployment capabilities. In addition to basing a third of the Fleet Marine Force in Japan, Marine expeditionary units (MEU) are typically stationed at sea so they can function as first responders to international incidents. To aid rapid deployment, the Maritime Pre-Positioning System was developed: Fleets of container ships are positioned throughout the world with enough equipment and supplies for a marine expeditionary force to deploy for 30 days.

Two small manuals published during the 1930s established USMC doctrine in two areas. The Small Wars Manual laid the framework for Marine counterinsurgency operations from Vietnam to Iraq and Afghanistan while the Tentative Landing Operations Manual established the doctrine for the amphibious operations of World War II. "Operational Maneuver from the Sea" was the doctrine of power projection in 2006.

The United States Marine Corps traces its roots to the Continental Marines of the American Revolutionary War, formed by Captain Samuel Nicholas by a resolution of the Second Continental Congress on 10 November 1775, to raise two battalions of marines. This date is celebrated as the birthday of the Marine Corps. Nicholas was nominated to lead the Marines by John Adams. By December 1775, Nicholas raised one battalion of 300 men by recruitment in his home city of Philadelphia.

In January 1776, the Marines went to sea under the command of Commodore Esek Hopkins and in March undertook their first amphibious landing, the Battle of Nassau in the Bahamas, occupying the British port of Nassau for two weeks. On 3 January 1777, the Marines arrived at the Battle of Princeton attached to General John Cadwalader's brigade, where they had been assigned by General George Washington; by December 1776, Washington was retreating through New Jersey and, needing veteran soldiers, ordered Nicholas and the Marines to attach themselves to the Continental Army. The Battle of Princeton, where the Marines along with Cadwalader's brigade were personally rallied by Washington, was the first land combat engagement of the Marines; an estimated 130 marines were present at the battle.

At the end of the American Revolution, both the Continental Navy and Continental Marines were disbanded in April 1783. The institution was resurrected on 11 July 1798; in preparation for the Quasi-War with France, Congress created the United States Marine Corps. Marines had been enlisted by the War Department as early as August 1797 for service in the newly-built frigates authorized by the Congressional "Act to provide a Naval Armament" of 18 March 1794, which specified the numbers of marines to recruit for each frigate.

The Marines' most famous action of this period occurred during the First Barbary War (1801–1805) against the Barbary pirates, when William Eaton and First Lieutenant Presley O'Bannon led 8 marines and 500 mercenaries in an effort to capture Tripoli. Though they only reached Derna, the action at Tripoli has been immortalized in the Marines' Hymn and the Mameluke sword carried by Marine officers.

During the War of 1812, Marine detachments on Navy ships took part in some of the great frigate duels that characterized the war, which were the first and last engagements of the conflict. Their most significant contribution was holding the center of General Andrew Jackson's defensive line at the 1815 Battle of New Orleans, the final major battle and one of the most one-sided engagements of the war. With widespread news of the battle and the capture of HMS Cyane, HMS Levant and HMS Penguin, the final engagements between British and U.S. forces, the Marines had gained a reputation as expert marksmen, especially in defensive and ship-to-ship actions. They played a large role in the 1813 defense of Sacket's Harbor, New York and Norfolk and Portsmouth, Virginia, also taking part in the 1814 defense of Plattsburgh in the Champlain Valley during one of the final British offensives along the Canadian-U.S. border. The Battle of Bladensburg, fought 24 August 1814, was one of the worst days for American arms, though a few units and individuals performed heroic service. Notable among them were Commodore Joshua Barney's 500 sailors and the 120 marines under Captain Samuel Miller USMC, who inflicted the bulk of British casualties and were the only effective American resistance during the battle. A final desperate Marine counter attack, with the fighting at close quarters, however was not enough; Barney and Miller's forces were overrun. In all of 114 marines, 11 were killed and 16 wounded. During the battle Captain Miller's arm was badly wounded, for his gallant service in action, Miller was brevetted to the rank of Major USMC.

After the war, the Marine Corps fell into a malaise that ended with the appointment of Archibald Henderson as its fifth commandant in 1820. Under his tenure, the Corps took on expeditionary duties in the Caribbean, the Gulf of Mexico, Key West, West Africa, the Falkland Islands, and Sumatra. Commandant Henderson is credited with thwarting President Jackson's attempts to combine and integrate the Marine Corps with the Army. Instead, Congress passed the Act for the Better Organization of the Marine Corps in 1834, stipulating that the Corps was part of the Department of the Navy as a sister service to the Navy.

Commandant Henderson volunteered the Marines for service in the Seminole Wars of 1835, personally leading nearly half of the entire Corps (two battalions) to war. A decade later, in the Mexican–American War (1846–1848), the Marines made their famed assault on Chapultepec Palace in Mexico City, which would be later celebrated as the "Halls of Montezuma" in the Marines' Hymn. In fairness to the U.S. Army, most of the troops who made the final assault at the Halls of Montezuma were soldiers and not Marines. The Americans forces were led by Army General Winfield Scott. Scott organized two storming parties of about 250 men each for 500 men total including 40 marines.

In the 1850s, the Marines engaged in service in Panama and Asia and were attached to Commodore Matthew Perry's East India Squadron on its historic trip to the Far East.

The Marine Corps played a small role in the Civil War (1861–1865); their most prominent task was blockade duty. As more and more states seceded from the Union, about a third of the Corps's officers left the United States to join the Confederacy and form the Confederate States Marine Corps, which ultimately played little part in the war. The battalion of recruits formed for the First Battle of Bull Run performed poorly, retreating with the rest of the Union forces. Blockade duty included sea-based amphibious operations to secure forward bases. In early November 1861, a group of sailors and Marines landed in the towns of Port Royal and Beaufort, South Carolina. A few days later that task force captured nearby Hilton Head Island. A couple of weeks later a reconnaissance in force group captured Tybee Island. This is where the Union set up the artillery barrage to bombard Fort Pulaski. In April and May 1862, Marines participated in the capture and occupation of New Orleans and the occupation of Baton Rouge, Louisiana, key events in the war that helped secure Union control of the lower Mississippi River basin and denied the Confederacy a major port and naval base on the Gulf Coast.

The remainder of the 19th century was marked by declining strength and introspection about the mission of the Marine Corps. The Navy's transition from sail to steam put into question the need for Marines on naval ships. Meanwhile, Marines served as a convenient resource for interventions and landings to protect American interests overseas. The Corps was involved in over 28 separate interventions in the 30 years from the end of the American Civil War to the end of the 19th century. They were called upon to stem political and labor unrest within the United States. Under Commandant Jacob Zeilin's tenure, Marine customs and traditions took shape: the Corps adopted the Marine Corps emblem on 19 November 1868. It was during this time that "The Marines' Hymn" was first heard. Around 1883, the Marines adopted their current motto "Semper fidelis" (Always Faithful). John Philip Sousa, the musician and composer, enlisted as a Marine apprentice at age 13, serving from 1867 until 1872, and again from 1880 to 1892 as the leader of the Marine Band.

During the Spanish–American War (1898), Marines led American forces ashore in the Philippines, Cuba, and Puerto Rico, demonstrating their readiness for deployment. At Guantánamo Bay, Cuba, the Marines seized an advanced naval base that remains in use today. Between 1899 and 1916, the Corps continued its record of participation in foreign expeditions, including the Philippine–American War, the Boxer Rebellion in China, Panama, the Cuban Pacifications, the Perdicaris incident in Morocco, Veracruz, Santo Domingo, and the Banana Wars in Haiti and Nicaragua; the experiences gained in counterinsurgency and guerrilla operations during this period were consolidated into the Small Wars Manual.

During World War I, Marines served as a part of the American Expeditionary Force under General John J. Pershing when America entered into the war on 6 April 1917. The Marine Corps had a deep pool of officers and non-commissioned officers with battle experience and thus experienced a large expansion. The U.S. Marine Corps entered the war with 511 officers and 13,214 enlisted personnel and by 11 November 1918 had reached a strength of 2,400 officers and 70,000 enlisted. African-Americans were entirely excluded from the Marine Corps during this conflict. Opha May Johnson was the first woman to enlist in the Marines; she joined the Marine Corps Reserve in 1918 during World War I, officially becoming the first female Marine. From then until the end of World War I, 305 women enlisted in the Corps. During the Battle of Belleau Wood in 1918, the Marines and U.S. media reported that Germans had nicknamed them Teufel Hunden, meaning "Devil Dogs" for their reputation as shock troops and marksmen at ranges up to 900 meters; there is no evidence of this in German records (as Teufelshunde would be the proper German phrase). Nevertheless, the name stuck in U.S. Marine lore.

Between the World Wars, the Marine Corps was headed by Commandant John A. Lejeune, and under his leadership, the Corps studied and developed amphibious techniques that would be of great use in World War II. Many officers, including Lieutenant Colonel Earl Hancock "Pete" Ellis, foresaw a war in the Pacific with Japan and undertook preparations for such a conflict. Through 1941, as the prospect of war grew, the Corps pushed urgently for joint amphibious exercises with the Army and acquired amphibious equipment that would prove of great use in the upcoming conflict.

In World War II, the Marines performed a central role in the Pacific War, along with the U.S. Army. The battles of Guadalcanal, Bougainville, Tarawa, Guam, Tinian, Cape Gloucester, Saipan, Peleliu, Iwo Jima, and Okinawa saw fierce fighting between marines and the Imperial Japanese Army. Some 600,000 Americans served in the U.S. Marine Corps in World War II.

The Battle of Iwo Jima, which began on 19 February 1945, was arguably the most famous Marine engagement of the war. The Japanese had learned from their defeats in the Marianas Campaign and prepared many fortified positions on the island including pillboxes and network of tunnels. The Japanese put up fierce resistance, but American forces reached the summit of Mount Suribachi on 23 February. The mission was accomplished with high losses of 26,000 American casualties and 22,000 Japanese.

The Marines played a comparatively minor role in the European theater. Nonetheless, they did continue to provide security detachments to U.S. embassies and ships, contributed personnel to small special ops teams dropped into Nazi-occupied Europe as part of Office of Strategic Services (OSS, the precursor to the CIA) missions, and acted as staff planners and trainers for U.S. Army amphibious operations, including the Normandy landings.

By the end of the war, the Corps had expanded from two brigades to six divisions, five air wings, and supporting troops, totaling about 485,000 marines. In addition, 20 defense battalions and a parachute battalion were raised. Nearly 87,000 marines were casualties during World War II (including nearly 20,000 killed), and 82 were awarded the Medal of Honor.

In 1942, the Navy Seabees were created with the Marine Corps providing their organization and military training. Many Seabee units were issued the USMC standard issue and were re-designated "Marine". Despite the Corps giving them their military organization and military training, issuing them uniforms, and redesignating their units, the Seabees remained Navy. USMC historian Gordon L. Rottmann writes that one of the "Navy's biggest contributions to the Marine Corps during WWII was the creation of the Seabees."

Despite Secretary of the Navy James Forrestal's prediction that the Marine flag raising at Iwo Jima meant "a Marine Corps for the next five hundred years", the Corps faced an immediate institutional crisis following the war because of a suddenly shrunken budget. Army generals pushing for a strengthened and reorganized defense establishment attempted to fold the Marine mission and assets into the Navy and Army. Drawing on hastily assembled Congressional support, and with the assistance of the so-called "Revolt of the Admirals", the Marine Corps rebuffed such efforts to dismantle the Corps, resulting in statutory protection of the Marine Corps in the National Security Act of 1947. Shortly afterward, in 1952 the Douglas–Mansfield Act afforded the commandant an equal voice with the Joint Chiefs of Staff on matters relating to the Marines and established the structure of three active divisions and air wings that remain today.

The beginning of the Korean War (1950–1953) saw the hastily formed Provisional Marine Brigade holding the defensive line at the Pusan Perimeter. To execute a flanking maneuver, General Douglas MacArthur called on United Nations forces, including U.S. Marines, to make an amphibious landing at Inchon. The successful landing resulted in the collapse of North Korean lines and the pursuit of North Korean forces north near the Yalu River until the entrance of the People's Republic of China into the war. Chinese troops surrounded, surprised, and overwhelmed the overextended and outnumbered American forces. The U.S. Army's X Corps, which included the 1st Marine Division and the Army's 7th Infantry Division regrouped and inflicted heavy casualties during their fighting withdrawal to the coast, known as the Battle of Chosin Reservoir.

The fighting calmed after the Battle of the Chosin Reservoir, but late in March 1953, the relative quiet of the war was broken when the People's Liberation Army launched a massive offensive on three outposts manned by the 5th Marine Regiment. These outposts were codenamed "Reno", "Vegas", and "Carson". The campaign was collectively known as the Nevada Cities Campaign. There was brutal fighting on Reno Hill, which was eventually captured by the Chinese. Although Reno was lost, the 5th Marines held both Vegas and Carson through the rest of the campaign. In this one campaign, the Marines suffered approximately 1,000 casualties and might have suffered much more without the U.S. Army's Task Force Faith. Marines would continue a battle of attrition around the 38th Parallel until the 1953 armistice. During the war, the Corps expanded from 75,000 regulars to a force of 261,000 marines, mostly reservists; 30,544 marines were killed or wounded during the war, and 42 were awarded the Medal of Honor.

The Marine Corps served in the Vietnam War, taking part in such battles as the Battle of Hue and the Battle of Khe Sanh in 1968. Individuals from the USMC generally operated in the Northern I Corps Regions of South Vietnam. While there, they were constantly engaged in a guerrilla war against the Viet Cong, along with an intermittent conventional war against the North Vietnamese Army, this made the Marine Corps known throughout Vietnam and gained a frightening reputation from the Viet Cong. Portions of the Corps were responsible for the less-known Combined Action Program that implemented unconventional techniques for counterinsurgency and worked as military advisors to the Republic of Vietnam Marine Corps. Marines were withdrawn in 1971 and returned briefly in 1975 to evacuate Saigon and attempt a rescue of the crew of the SS Mayaguez. Vietnam was the longest war up to that time for the Marines; by its end, 13,091 had been killed in action, 51,392 had been wounded, and 57 Medals of Honor had been awarded. Because of policies concerning rotation, more marines were deployed for service during Vietnam than World War II.

While recovering from Vietnam, the Corps hit a detrimental low point in its service history caused by courts-martial and non-judicial punishments related partially to increased unauthorized absences and desertions during the war. Overhaul of the Corps began in the late 1970s, discharging the most delinquent, and once the quality of new recruits improved, the Corps focused on reforming the non-commissioned officer Corps, a vital functioning part of its forces.

After the Vietnam War, the U.S. Marines resumed their expeditionary role, participating in the failed 1980 Iran hostage rescue attempt Operation Eagle Claw, the Operation Urgent Fury and the Operation Just Cause. On 23 October 1983, the Marine barracks in Beirut was bombed, causing the highest peacetime losses to the Corps in its history (220 marines and 21 other service members were killed) and leading to the American withdrawal from Lebanon. In 1990, Marines of the Joint Task Force Sharp Edge saved thousands of lives by evacuating British, French and American nationals from the violence of the Liberian Civil War.

During the Persian Gulf War of 1990 to 1991, Marine task forces formed for Operation Desert Shield and later liberated Kuwait, along with Coalition forces, in Operation Desert Storm. Marines participated in combat operations in Somalia (1992–1995) during Operations Restore Hope, Restore Hope II, and United Shield to provide humanitarian relief. In 1997, Marines took part in Operation Silver Wake, the evacuation of American citizens from the U.S. Embassy in Tirana, Albania.

Following the attacks on 11 September 2001, President George W. Bush announced the Global War on Terrorism. The stated objective of the Global War on Terror is "the defeat of Al-Qaeda, other terrorist groups and any nation that supports or harbors terrorists". Since then, the Marine Corps, alongside the other military services, has engaged in global operations around the world in support of that mission.

In spring 2009, President Barack Obama's goal of reducing spending in the Defense Department was led by Secretary Robert Gates in a series of budget cuts that did not significantly change the Corps's budget and programs, cutting only the VH-71 Kestrel and resetting the VXX program. However, the National Commission on Fiscal Responsibility and Reform singled the Corps out for the brunt of a series of recommended cuts in late 2010. In light of budget sequestration in 2013, General James Amos set a goal of a force of 174,000 Marines. He testified that this was the minimum number that would allow for an effective response to even a single contingency operation, but it would reduce the peacetime ratio of time at home bases to time deployed down to a historical low level.

Marines and other American forces began staging in Pakistan and Uzbekistan on the border of Afghanistan as early as October 2001 in preparation for Operation Enduring Freedom. The 15th and 26th Marine Expeditionary Units were some of the first conventional forces into Afghanistan in support of Operation Enduring Freedom in November 2001.

After that, Marine battalions and squadrons rotated through, engaging the Taliban and Al-Qaeda forces. Marines of the 24th Marine Expeditionary Unit flooded into the Taliban-held town of Garmsir in Helmand Province on 29 April 2008, in the first major American operation in the region in years. In June 2009, 7,000 marines with the 2nd Marine Expeditionary Brigade (2nd MEB) deployed to Afghanistan in an effort to improve security and began Operation Strike of the Sword the next month. In February 2010, the 2nd MEB launched the largest offensive of the Afghan Campaign since 2001, the Battle of Marjah, to clear the Taliban from their key stronghold in Helmand Province. After Marjah, marines progressed north up the Helmand River and cleared the towns of Kajahki and Sangin. Marines remained in Helmand Province until 2014.

U.S. Marines served in the Iraq War, along with its sister services. The I Marine Expeditionary Force, along with the U.S. Army's 3rd Infantry Division, spearheaded the 2003 invasion of Iraq. The Marines left Iraq in the summer of 2003 but returned in the beginning of 2004. They were given responsibility for the Al Anbar Province, the large desert region to the west of Baghdad. During this occupation, the Marines lead assaults on the city of Fallujah in April (Operation Vigilant Resolve) and November 2004 (Operation Phantom Fury) and saw intense fighting in such places as Ramadi, Al-Qa'im and Hīt. The service's time in Iraq courted controversy with events such as the Haditha killings and the Hamdania incident. The Anbar Awakening and 2007 surge reduced levels of violence. The Marine Corps officially ended its role in Iraq on 23 January 2010 when it handed over responsibility for Al Anbar Province to the U.S. Army. Marines returned to Iraq in the summer of 2014 in response to growing violence there.

Throughout the Global War on Terrorism, the U.S. Marines have supported operations in Africa to counter Islamic extremism and piracy in the Red Sea. In late 2002, Combined Joint Task Force – Horn of Africa was stood up at Camp Lemonnier, Djibouti to provide regional security. Despite transferring overall command to the Navy in 2006, the Marines continued to operate in the Horn of Africa into 2007.

In the 2020s, as the U.S. national strategy shifted from the war on terrorism to competition with China, the Marine Corps abandoned its previous plan to focus on land operations and strengthened its firepower configuration in the Indo-Pacific region to defeat the Chinese People's Liberation Army in possible island operations. As part of this shift the USMC has established a joint deployment with the Australian military in Darwin starting with 200 Marines in 2011.

The Department of the Navy, led by the Secretary of the Navy, is a military department of the cabinet-level U.S. Department of Defense that oversees the Marine Corps and the Navy. The most senior Marine officer is the Commandant (unless a Marine officer is the Chairman of the Joint Chiefs or Vice Chairman of the Joint Chiefs), responsible to the Secretary of the Navy for organizing, recruiting, training, and equipping the Marine Corps so that its forces are ready for deployment under the operational command of the combatant commanders. The Marine Corps is organized into four principal subdivisions: Headquarters Marine Corps (HQMC), the Operating Forces, the Supporting Establishment, and the Marine Forces Reserve (MARFORRES or USMCR).

The Headquarters Marine Corps (HQMC) consists of the Commandant of the Marine Corps, the Assistant Commandant of the Marine Corps, the Director Marine Corps Staff, the several Deputy Commandants, the Sergeant Major of the Marine Corps, and various special staff officers and Marine Corps agency heads that report directly to either the Commandant or Assistant Commandant. HQMC is supported by the Headquarters and Service Battalion, USMC providing administrative, supply, logistics, training, and services support to the Commandant and his staff. Additionally, Marine Corps' aircraft arm and intelligence arm are both organized under HQMC; those being the Marine Corps Aviation and Marine Corps Intelligence respectively.

The Operating Forces are divided into three categories: Marine Corps Forces (MARFOR) assigned to unified combatant commands, namely, the Fleet Marine Forces (FMF); Security Forces guarding high-risk naval installations; and Security Guard detachments at American embassies. Under the "Forces for Unified Commands" memo, in accordance with the Unified Command Plan, Marine Corps Forces are assigned to each of the combatant commands at the discretion of the secretary of defense. Since 1991, the Marine Corps has maintained component headquarters at each of the regional unified combatant commands.

Marine Corps Forces are divided into Forces Command (MARFORCOM) and Pacific Command (MARFORPAC), each headed by a lieutenant general dual-posted as the commanding general of either FMF Atlantic (FMFLANT) or FMF Pacific (FMFPAC), respectively. MARFORCOM/FMFLANT has operational control of the II Marine Expeditionary Force; MARFORPAC/FMFPAC has operational control of the I Marine Expeditionary Force and III Marine Expeditionary Force.

Additional service components under the Marine Corps Forces includes: the Marine Corps Forces Europe and Africa (MARFOREUR/AF) under U.S. European Command (EURCOM) and U.S. Africa Command (AFRICOM); the Marine Corps Forces Central Command (MARFORCENT) under U.S. Central Command (CENTCOM); the Marine Corps Forces South (MARFORSOUTH) under U.S. Southern Command (SOUTHCOM); the Marine Corps Forces Cyberspace Command (MARFORCYBER) under U.S. Cyber Command (CYBERCOM); the Marine Corps Forces Space Command (MARFORSPACE) under U.S. Space Command (SPACECOM); and the Marine Corps Forces Strategic Command (MARFORSTRAT) under U.S. Strategic Command (STRATCOM).

The basic framework for deployable Marine units is the Marine Air-Ground Task Force (MAGTF), a flexible structure of varying size. A MAGTF integrates a ground combat element (GCE), an aviation combat element (ACE), and a logistics combat element (LCE) under a common command element (CE), capable of operating independently or as part of a larger coalition. The MAGTF structure reflects a strong preference in the Corps toward self-sufficiency and a commitment to combined arms, both essential assets to an expeditionary force.

The Supporting Establishment includes the Combat Development Command, the Logistics Command, the Systems Command, the Training and Education Command (including Recruiting Command), the Installations Command, the Marine Band, and the Marine Drum and Bugle Corps.

The Marine Corps operates many major bases, 14 of which host operating forces, seven support and training installations, as well as satellite facilities. Marine Corps bases are concentrated around the locations of the Marine Expeditionary Forces, though reserve units are scattered throughout the US. The principal bases are Camp Pendleton on the West Coast, home to I Marine Expeditionary Force, Camp Lejeune on the East Coast, home to II Marine Expeditionary Force, and Camp Butler in Okinawa, Japan, home to III Marine Expeditionary Force.

Other important bases include air stations, recruit depots, logistics bases, and training commands. Marine Corps Air Ground Combat Center Twentynine Palms in California is the Marine Corps's largest base and home to the Corps's most complex combined-arms live-fire training. Marine Corps Base Quantico in Virginia is home to Marine Corps Combat Development Command and nicknamed the "Crossroads of the Marine Corps". The Marine Corps maintains a significant presence in the National Capital Region, with Headquarters Marine Corps scattered amongst the Pentagon, Henderson Hall, Washington Navy Yard, and Marine Barracks, Washington, D.C. Additionally, Marines operate detachments at many installations owned by other branches to better share resources, such as specialty schools. Marines are also present at and operate many forward bases during expeditionary operations.

The Marine Forces Reserve (MARFORRES/USMCR) consists of the Force Headquarters Group, 4th Marine Division, 4th Marine Aircraft Wing, and the 4th Marine Logistics Group. The MARFORRES/USMCR is capable of forming a 4th Marine Expeditionary Force or reinforcing/augmenting active-duty forces.

Marine Forces Special Operations Command (MARSOC) includes the Marine Raider Regiment, the Marine Raider Support Group, and the Marine Raider Training Center (MRTC). Both the Raider Regiment and the Raider Support Group consist of a headquarters company and three operations battalions. MRTC conducts screening, assessment, selection, training and development functions for MARSOC units. Marine Corps Special Operations Capable forces include: Air Naval Gunfire Liaison Companies, the Chemical Biological Incident Response Force, the Marine Division Reconnaissance Battalions, Force Reconnaissance Companies, Maritime Special Purpose Force, and Special Reaction Teams. Additionally, all deployed MEUs are certified as "special operations capable", namely, "MEU(SOC)".

Although the notion of a Marine special operations forces contribution to the United States Special Operations Command (USSOCOM) was considered as early as the founding of USSOCOM in the 1980s, it was resisted by the Marine Corps. Commandant Paul X. Kelley expressed the belief that marines should only support marines and that the Corps should not fund a special operations capability that would not directly support Marine Corps operations. However, much of the resistance from within the Corps dissipated when Marine leaders watched the Corps' 15th and 26th MEU(SOC)s "sit on the sidelines" during the very early stages of Operation Enduring Freedom while other conventional units and special operations units from the Army, Navy, and Air Force actively engaged in operations in Afghanistan. After a three-year development period, the Corps agreed in 2006 to supply a 2,500-strong unit, Marine Forces Special Operations Command, which would answer directly to USSOCOM.