In 1933, Hewitt took command of Destroyer Division 12. He was promoted to captain the next year. Hewitt then commanded the cruiser Indianapolis. In December 1939, he took over Cruiser Division 8. He was promoted to rear admiral in December 1940 and commanded task groups on neutrality patrols in the Atlantic. Following U.S. entry into the war in December 1941, in April 1942 Hewitt assumed command of the Amphibious Force, Atlantic Fleet. As such, he was responsible for U.S. amphibious forces in the Atlantic and Europe. Hewitt was the U.S. naval officer most involved in the development of amphibious doctrine in the Mediterranean and European Theaters during the war. He had charge of every major Allied amphibious operation in the Mediterranean Theater during the war.
Hewitt was promoted to vice admiral in November 1942, and in March 1943 he assumed command of the U.S. Navy Eighth Fleet. Working within an Allied command structure in which he was subordinate to the British Admiral Sir Andrew Browne Cunningham, and forced to coordinate military and naval operations and deal with such forceful characters as Major General George S. Patton, Hewitt demonstrated considerable diplomatic ability. Hewitt's mathematical and logistical skills were equally fully exercised in planning and directing complicated large-scale landing operations, reinforced by naval gunfire support, in North Africa (November 1942), Sicily (July 1943), Salerno (September 1943), and southern France (1944). His most difficult decision was whether to proceed with Operation torch, the North African landings, despite adverse weather conditions. He elected to proceed, a difficult choice that led to military success.
Promoted to full admiral in April 1945, shortly afterward Hewitt assumed command of the Twelfth Fleet, U.S. naval forces in European waters. He returned to the United States in October 1946 and took a special assignment at the Naval War College in Rhode Island before becoming naval representative to the United Nations Military Staff Committee. Hewitt retired in March 1949 and died at Middlebury, Vermont, on 15 September 1972.
Belot, Raymond de. The Struggle for the Mediterranean, 1939–1945. Princeton, NJ: Princeton University Press, 1951.; Hewitt, H. Kent. The Memoirs of Admiral H. Kent Hewitt. Edited by Evelyn M. Cherpak. Newport, RI: Naval War College Press, 2002.; Jones, Matthew. Britain, the United States, and the Mediterranean War, 1942–1944. New York: St. Martin's Press, 1996.; Morison, Samuel Eliot. History of United States Naval Operations in World War II. Vol. 5, The Struggle for Guadalcanal, August 1942–February 1943. Boston: Little, Brown, 1949.; Morison, Samuel Eliot. History of United States Naval Operations in World War II. Vol. 11, The Invasion of France and Germany, 1944–1945. Boston: Little, Brown, 1957.; Morison, Samuel Eliot. History of United States Naval Operations in World War II. Vol. 9, Sicily, Salerno, Anzio (January 1943–June 1944). Boston: Little, Brown, 1954.; 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.