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 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 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 of “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. 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 Corps’ traditional missions, it has renewed an emphasis on amphibious capabilities.