Admiral MacDonald had a varied career that included tours as an aide at the White House just prior to U.S. involvement in World War II and as a special naval observer at the American Embassy in London, where he witnessed the Battle of Britain and the bombing of London. He served as executive officer of the USS O'Bannon (DD-450) during the capture and defense of Guadalcanal, and later commanded the ship. During the rest of the war he held positions on the staffs of Commander in Chief U.S. Fleet, Commander U.S. Naval Forces France, and finally served on the staff of Commander Naval Forces Germany. After his return, he commanded the presidential yacht Williamsburg (AGC-369), which provided him a great deal of insight into the personality of President Harry Truman. Later tours included head of the foreign language department at the Naval Academy, command of a destroyer squadron, and duty as assistant director of the undersea warfare department of OpNav, from which position he retired in October 1959.