Fleet, aboard the battleship . World War I As a part of the new full-time staff in the First Naval District, Boston, in 1918, Deyo taught destroyer seamanship. He was assigned the year after Rear Admiral Albert Gleaves, then Commander, Destroyer Force, Atlantic Fleet, became Commander of United States Convoy Operations in the Atlantic in addition to his other duties. He was next transferred to the troopship Northern Pacific as a part of its regular USN officer complement. World War I's movement of a million men and their supplies was unprecedented. The crews of harbor and pilot boats, inshore scouts and patrol craft, new merchantmen, escorting vessels, all required training. In the First Naval District, Deyo was a part of the destroyer piece. Interwar 1920s Pacific Deyo was attached to Admiral Samuel Robison's personal staff of ten officers aboard the in 1925–1926. Now a Lieutenant Commander, Deyo was the most junior officer as Flag Lieutenant. The next rung up the ladder was the Assistant Chief of Staff, then Commander Chester W. Nimitz. Following early armored cruiser service in the Caribbean, World War I destroyer service operating in the North Atlantic, and cruiser service crossing the Pacific, Deyo was assigned to a three-year tour teaching seamanship at the Naval Academy, 1926–1929. He was appointed during the tenure of Superintendent Rear Admiral Louis M. Nulton and completed his tour under Rear Admiral Samuel S. Robison with whom he had served in the Dominican Republic. He returned to sea to take command of the destroyer . His exemplary promise as a commander at sea resulted in an appointment to the Naval War College staff immediately following his study there. He then returned to sea in 1934 as the Executive Officer aboard the light cruiser . 1930s Pacific World War II in the Atlantic With accumulating experience in escort service in the Atlantic, fleet staff service crossing the Pacific, and Asiatic Squadron staff duty for operations and war plans during Japanese expansion, Deyo was prepared for Main Navy assignments from 1939 to 1941 as the Navy's assistant hydographer, then aide to the Secretary of the Navy until war sent him to sea again. Then a Captain, Deyo was escort commander of Task Unit 4.1.1 and the Commodore of Destroyer Squadron 11. His group was tasked to escort 44 merchant ships ranging from a luxury liner to a rusty ship of the Levant. His pennant