Defense secretary Bob Gates fired the Air Force's two top military and civilian leaders Thursday. Gates says they are responsible for the historic Pentagon shake-up after embarrassing nuclear mix-ups.

Air Force Chief of Staff Gen. Michael Moseley and Air Force Secretary Michael Wynne both handed in their resignations after the results of an investigation regarding a mistaken shipment to Taiwan of four Air Force electrical fuses for ballistic missile warheads.

Firings of this caliber are highly unusual, but Gates said it had to be done.