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.
The late 19th and 20th da, 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 bro. Marines would develop 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. They often were assigned to man anti-aircraft batteries.