39th President Jimmy Carter: Navy, Liutenant; was assigned to the sub Pomfret SS-391 and soon was promoted to lieutenant, junior grade. After doing graduate work in physics at Union College, he served as executive officer aboard the submarine K-1 (SSK 1), the first postwar submarine built, and was promoted to lieutenant. But in 1952, Carter was detached from the K-1 to participate, under then-Capt. Hyman Rickover, on the design and development of nuclear propulsion plants for naval vessels. In October 1953, Carter was training the crew of the submarine Seawolf in use of these plants when his father died. At his own request, Lt. James Earl Carter Jr. was honorably discharged after seven years, four months, and eight days of active duty. He remained on reserve duty until 1961.