In the third Star Trek trailer, Pike tells Kirk that his father was a starship captain for 12 minutes and saved 800 lives. Right there you figure that George Kirk's career ended quite badly:
CAPTAIN GEORGE KIRK: Sir! I pleased to report in my 12th minute as captain, I have saved 800 lives.
ADMIRAL: You were supposed to save 2000 lives. Where are the other 1200?
CAPTAIN GEORGE KIRK: Ummm....
ADMIRAL: Your services are no longer required.