"Kill'em all, and let God sort'em out" is adopted by the Marines and the Green Berets. I think it derives from "Neca eos omnes. Deus suos agnoset", or "Kill them all. God will know His own.". This was a misunderstood reference to 2 Tim. 2:19 which in part reads, "The Lord knoweth them that are his". I think this comes from around 1210AD, when Pope Innocent III unleashed "orders of fire and sword" against heretics throughout Europe. In this process there was a terrible massacre at the city Beziers, where it was thought that over 100,000 people were killed. After that city where taken, they had captured over 450 "heretics", but many of them claimed to be good Catholics. The quote is believed to be first used here, when they killed all the "heretics". It did not matter if they killed good people, because if one led a godly life, God would know of it, and the reward would be eternal paradise anyway.
