United States Marine Corps 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 the 1850s, the Marines would see further service in Panama and Asia, attached to 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' officers left the United
Organization of the United States Marine Corps Marine forces assigned to Unified Combatant Commands, Marine Corps Security Forces guarding naval installations, and Marine Security Guard detachments at American embassies. Under the "Forces for Unified Commands" memo, Marine forces are assigned to each of the regional unified combatant commands at the discretion of the Secretary of Defense and with the approval of the President. Since 1991, the Marine Corps has maintained component headquarters at each of the regional unified combatant commands. Marine Corps Forces are further divided into Marine Forces Command (consisting of II Marine Expeditionary Force) and Marine Forces Pacific (I Marine Expeditionary Force and III Marine