Between the world wars, Hart commanded submarine and cruiser forces and the battleship Mississippi. He graduated from the Naval War College in 1923 and the Army War College in 1924. In 1929, Hart was promoted to rear admiral and took command of submarines in the Atlantic and Pacific Fleets from 1929 to 1931. He was superintendent of the Naval Academy from 1931 to 1934. He commanded a cruiser division of the Scouting Force from 1934 to 1936 and served as a member of the navy's General Board from 1936 to 1939.
In June 1939, Hart was promoted to full admiral and given command of the small U.S. Asiatic Fleet. During the next years, he accelerated fleet training and drills and made plans to defend the Philippine Islands and to cooperate with the British and Dutch if war broke out with Japan. Lacking the resources to counter the Japanese invasion of the Philippines in December 1941 and denied air support from the U.S. Army's Far East Air Force, Hart sent his surface units to the Netherlands East Indies (NEI) at the end of the month and moved his headquarters to Java.
In January 1942, Hart was appointed commander of the naval forces of the American-British-Dutch-Australian Command (ABDACOM), which was charged with defending the NEI. Hart had no chance of success, for his resources were limited and he had no prospect of reinforcements. Moreover, the British and Dutch disagreed with his plans for using his ships. At the end of January, Hart sent his cruisers and destroyers against Japanese forces in the Battle of Makassar Strait, but the Dutch wished to concentrate ABDACOM's ships for the defense of Java. As a result, in February 1942, Hart relinquished his command to Vice Admiral C. E. L. Helfrich of the Netherlands navy and returned to the United States. Later that month, most of ABDACOM's ships were lost in the Battle of the Java Sea.
Hart served with the General Board until his retirement in February 1945, when he was appointed a U.S. senator from Connecticut, a post he held until 1947. Hart died in Sharon, Connecticut, on 4 July 1971.
John Kennedy Ohl
Leutze, James. A Different Kind of Victory: A Biography of Thomas C. Hart. Annapolis, MD: Naval Institute Press, 1981.; Morison, Samuel Eliot. History of United States Navy Operations in World War II. Vol. 3, The Rising Sun in the Pacific, 1931–April 1942. Boston: Little, Brown, 1948.; Morton, Louis. United States Army in World War II: The War in the Pacific: The Fall of the Philippines. Washington, DC: Office of the Chief of Military History, 1953.; Truscott, Lucian K., Jr. The Twilight of the U.S. Cavalry: Life in the Old Army, 1917–1942. Edited and with Preface by Lucian K. Truscott III and Foreword by Edward M. Coffman. Lawrence: University Press of Kansas, 1989.