Truman served with an artillery Battery in WW I. That's about it until Eisenhower (duh!), JFK-Navy, Pacific Theatre, Nixon-Navy, Pacific Theatre...not sure about LBJ or Gerald Ford. Who's next? Reagan wanted to go but was counseled that he could do more by promoting support a here at home. George Bush I was a Naval Aviator; shot down off Chichi Jima ( a few hundred miles north of Iwo Jima) and the book 'Flyboys' details that episode. GW Bush was Air National Guard. Clinton was a dope smoker and shirt chaser. Did I miss anyone?