LTJG Kennedy (standing at far right) with his crew on PT-109 in 1943.

On this day in 1943, future President John F. Kennedy was serving as the
commander of a torpedo boat in the Solomon Islands when his ship was
fired upon by the Japanese navy.   
 

As a young man, Kennedy had desperately wanted to go into the Navy but
was originally rejected because of chronic health problems, particularly a
back injury he had sustained playing football while attending Harvard
University. In 1941, though, his politically connected father used his
influence to get Jack, as he  was called, into the Navy. In 1942,
Kennedy volunteered for PT (motorized torpedo) boat duty in the
Pacific.