In contrast to the British attitude, the U.S. military, especially the Marine Corps remained enthusiastic at the possibilities of amphibious warfare. The Marines Corps was searching for an expanded mission after World War I, during which it had merely been used as a junior version of the Army infantry. During the 1920s, it found a new mission — to be a fast-reacting, light infantry fighting force carried rapidly to far off locations by the US Navy. Its special role would be amphibious landings on enemy-held islands, but it took years to figure out how to do that. The Mahanian notion of a decisive fleet battle required forward bases for the Navy close to the enemy. After the Spanish–American War the Marines gained the mission of occupying and defending those forward bases, and began a training program on Culebra Island, Puerto Rico.