War Plan Orange
From June 1927 to April 1929, Horne served as chief assistant to Rear Admiral Frank Schofield, head of the War Plans Division of the Office of the Chief of Naval Operations. Horne's experience with aviation and as naval attaché in Tokyo proved invaluable when updating War Plan Orange, the prewar blueprint for a projected war with Japan. His "down-to-earth, old shoe" personality helped soothe relations with Army counterparts on the Joint Army and Navy Board.