Capabilities of US Marine Corps: The Marine Corps fulfills a vital role in national security as an amphibious, expeditionary, air-ground combined arms task force, capable of forcible entry from the air, land, and sea. It is capable of asymmetric warfare with conventional, irregular, and hybrid forces.

While the Marine Corps does not employ any unique combat arms, as a force it has the unique ability to 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 combat component under a common command element. While the creation of joint commands under the Goldwater–Nichols Act has improved inter-service coordination between each branch, the Corps' ability to permanently maintain integrated multi-element 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 around 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 that "Every Marine is a rifleman", a focus 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. Marines have demonstrated the value of this culture many times throughout history. For example, at Wake Island, when all of the Marine aircraft were shot down, pilots continued the fight as ground officers, leading supply clerks and cooks in a final defensive effort. As a result, a large degree of initiative and autonomy is expected of junior Marines, particularly the NCOs (corporals and sergeants), as compared with many other military organizations. The Marine Corps emphasizes authority and responsibility downward to a greater degree than the other military services. 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 the development of 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 Corp's traditional missions, it has 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. This allows the ability to function as first responders to international incidents. The United States Army now maintains light infantry units capable of rapid worldwide deployment, but those units do not match the combined-arms integration of a MAGTF and lack the logistics that the Navy provides. For this reason, the Marine Corps is often assigned to non-combat missions such as the evacuation of Americans from unstable countries and providing humanitarian relief during natural disasters. In larger conflicts, Marines act as a stopgap, to get into and hold an area until larger units can be mobilized. The Corps performed this role in World War I and the Korean War, where Marines were the first significant combat units deployed from the United States and held the line until the country could mobilize for war. 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.