 The 1919 plans incorporated a Mobile Naval Base Defence Organisation ( MNBDO ) which could develop and defend a forward base . The MNBDO had a strength of 7 @,@ 000 and included a brigade of antiaircraft artillery , a brigade of coastal artillery and a battalion of infantry , all drawn from the Royal Marines . In one paper exercise , the Royal Marines occupied Nakagusuku Bay unopposed and the MNBDO developed a major base there from which the fleet blockaded Japan . Actual fleet exercises were conducted in the Mediterranean in the 1920s to test the MNBDO concept . However , the Royal Marines were not greatly interested in amphibious warfare , and lacking organisational backing , the techniques and tactics of amphibious warfare began to atrophy . By the 1930s the Admiralty was concerned that the United States and Japan were well ahead of Britain in this field and persuaded the Army and RAF to join with it in establishing the Inter @-@ Service Training and Development Centre , which opened in July 1938 . Under its first commandant , Captain Loben Edward Harold Maund , it began investigating the problems of amphibious warfare , including the design of landing craft . 
