United States Marine Corps USMC

The Continental Congress authorized two battalions of Marines on November 10, 1775, the date still celebrated as the Corps' birthday, and Congress re-established the Marine Corps on July 11, 1798. Marines served aboard warships and landed ashore from Tripoli to Mexico City, and in the twentieth century the Corps developed amphibious assault, proving it in the Pacific campaigns of the Second World War at places such as Guadalcanal, Tarawa, and Iwo Jima. After proposals to fold it into the Army, Congress protected it by law in 1952, fixing its structure at three active divisions and air wings and giving the Commandant a role on the Joint Chiefs that became full membership in 1978.

The Marine Corps is a separate armed service inside the Department of the Navy, reporting to the Secretary of the Navy, with about 170,000 active duty Marines and roughly 30,000 more in its reserve. It is organized around Marine Air-Ground Task Forces, which combine infantry, aviation, and logistics under one commander, and its units deploy on Navy amphibious ships as a ready crisis force. Marines also guard U.S. embassies and fly the President's helicopter, and recruits train at Parris Island, South Carolina, and San Diego.

Since 2020 the Corps has reshaped itself under a plan called Force Design, retiring all its tanks, cutting some artillery and infantry, and building small, mobile units with anti-ship missiles meant to operate among islands in a conflict in the Pacific. Supporters say the changes prepare the Corps for war with a major power at sea, while critics, including retired generals, say they gave up the ability to handle the broad range of crises Marines have traditionally met. In 2025 Marines were also sent to Los Angeles during protests over immigration enforcement, part of a broader debate over the use of troops at home.