One of my friends likes to go off on rants about government conspiraces and secrets.
Normally I thnk he is a little too paranoid, but then I stopped to think about one of them.
He has a theory that it would be possible/likely for the military to have a specially engineered drug for their special forces.
I always thought it was a kinda out there theory, but then I remembered one of the theries for the origin or the word assassin,
http://en.wikipedia.org/wiki/Hashshashin, involved people using hash.
So if the idea for having warriors use drugs was around way back then maybe it isn't a stretch to think they may do it now.