War I as Director of Submarine Operations for the Navy Department. Serving in this office as its head until 1922, Hart fought doggedly to improve the lot of the submarine arm of the navy. His tenacity was responsible for the U.S. Navy's acquisition of surrendered German U-boats after World War I to learn the details of the technical innovations incorporated in the erstwhile enemy craft. Examination and trials of these U-boats were very influential in subsequent US Navy submarine design. He also was involved in the development of the Mark 6 torpedo exploder. After World War I, Hart commanded . From 1931–34, Hart was Superintendent of the United States Naval Academy. An unsuccessful recommendation of Hart's while on the General Board, beginning in 1936, was the building of small submarines. Hart's plan was to replace the aging S-boats, R-boats, and O-boats to provide area defense of submarine bases. This plan resulted in only two experimental submarines, and . During this period, Hart successfully advocated the building of large destroyer leaders, later classified as anti-aircraft light cruisers (CLAAs), which became the Atlanta class and others. World War II Hart was appointed commander in chief, U.S. Asiatic Fleet on July 25, 1939 and was promoted to admiral the same day. He held that position at the commencement of hostilities in World War II between Japan and the United States in December 1941. The majority of forces under Hart's command were located in the Philippines, with a small force of destroyers and a light cruiser based in Borneo. His command included the majority of the combat-ready US submarines in the Pacific. Hart initially commanded U.S. naval forces from Manila, but was forced to relocate to Java on January 15, 1942, in light of rapid Japanese advances through the Philippine archipelago. On his relocation to Java, Hart was named Commander, Naval Forces, ABDA Command, a joint British, Dutch, American and Australian military command, formed for purposes of holding the southern portions of the Dutch East Indies against further Japanese advances. While in command of ABDA naval forces, ships under his command fought the Battle of Balikpapan, a tactical victory, but strategic defeat for the allied forces. Hart held the command of the U.S. Navy Asiatic Fleet until February 5, 1942, at which point the command ceased to exist as part of a broader U.S. military command restructuring in the Southwest Pacific. Hart continued to