in the development of the first specialized landing crafts, including the Assault Landing Craft, the Mechanized Landing Craft (LCM(1)), the Landing Craft Tank (Mk. 1), Support Landing Craft LCS(1), LCS(2) and Landing Ship Infantry. Divisional-sized amphibious landing exercises were carried out by the British Army in the 1930s. United States In contrast to the British attitude, the U.S. military, especially the Marine Corps remained enthusiastic at the possibilities of amphibious warfare. The Marine 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. As early as 1900 the General Board of the United States Navy considered building advance bases for naval operations in the Pacific and the Caribbean. The Marine Corps was given this mission in 1920, but the challenge was to avoid another disaster like Gallipoli. The conceptual breakthrough came in 1921 when Major "Pete" Ellis wrote Advanced Base Operations in Micronesia a secret 30,000-word manifesto that proved inspirational to Marine strategists and highly prophetic. To win a war in the Pacific, the Navy would have to fight its way through thousands of miles of ocean controlled by the Japanese—including the Marshall, Caroline, Marianas and Ryukyu island chains. If the Navy could land Marines to seize selected islands, they could become forward bases. Ellis argued that with an enemy prepared to defend the beaches, success depended on high-speed movement of waves of assault craft, covered by heavy naval gunfire and attack from the air. He predicted that the decisive action would take place on the beach itself, so the assault teams would need not just infantry but also machine gun units, light artillery, light tanks, and combat engineers to defeat beach obstacles and defenses. Assuming the enemy had its own artillery, the landing craft would have to be specially built to