Call your broker to get the address for ballots submitted by courier (which would NOT be a PO box).
If I were in Afgahnistan, and I have a number of colleagues who are, I would get this out by courier today. Remember to write your broker's name and account number at the top of page 1 (Schwab told me to do this); I also wrote it at the top of pages 6 and 9 just to be safe.