A young Harry Truman once had a roommate in Kansas City named Eisenhower. No, not Dwight D. Eisenhower himself but one of his brothers.
Truman was an artillery officer in WW I. His unit was firing toward German lines at 11:00 am/11/11/1918.
In 1945, he orders the dropping of the atomic bomb to end WW II.
While unprovable, it is possible Harry Truman (in essence) fired the last shot of both World Wars.