Born on 1 July 1887 in Poughkeepsie, New York, he graduated from the United States Naval Academy in 1911. Deyo took his first assignment at sea aboard the battleship, USS Virginia in the Caribbean. As a part of the full time staff in the First Naval District, Boston, in 1918, Deyo taught destroyer seamanship. He was next transferred to the troopship ‘’Northern Pacific’’ as a part of its regular USN officer complement. Following early armored cruiser service in the Caribbean, World War I destroyer service operating in the North Atlantic, and cruiser service crossing the Pacific, Morton Deyo was assigned to a three-year tour teaching seamanship at the Naval Academy, 1926-1929. He returned to sea to take command of destroyer USS Sloat. On 6 June 1944, now Rear Admiral Deyo commanded the western Operation Neptune Force “U”, supporting the landing of the American First Army at Utah and Omaha beaches. Naval bombardment for the invasion of Southern France was commanded by Admiral Deyo. Admiral Deyo's crowning achievement in the Pacific was command of gunfire and covering force for the assault and occupation of Okinawa.