"Kill 'em all; let God sort 'em out"
Possibly it originates with a Crusader commander (1209)
"Caedite eos. Novit enim Dominus qui sunt eius.
...but for me the English version goes back to the US-Vietnam conflict that supposedly began during the JFK administration in 1961.
The first time I heard the English version was from USN and USMC personnel returning from Vietnam in the 70s and doing re-training with us at GLakes and Bainbridge. Many were pretenders, but others had "walked the walk". Some of them even had shoulder flashes such as this from old uniforms.
It was an unofficial slogan of MACV SOG. As far as I know the winged-skull was used by most most branches, but the flashes with the anchor were SEALs.
Later, I did some interviews (1990s) in Guatemala with some veterans (graduates of the Phoenix program), and as you can see the attitude prevailed ..
Paraphrasing from one and to the best of my memory...
" We had intel that said there were some URNG guys habiting there. We got there before dawn, and set up SAWs at the east and west of the ville, but the fucking dogs started barking... My guys went in from the garita... with a lot of noise and commotion. ...villagers went running up the hillside into the enfilade ...assholes never had a chance. I think we had a body-count of around 300, fuckin piece of art...guerilla?...who the fuck knows? ...let God sort it out..."
AFAIK, that particular engagement is still "under investigation". It is a matter of record that approximately 250,000 civilians lost their lives during the Civil War and genocide that lasted for almost 30 years in my country.
And I found this on ThisDayinQuotes,com...
More recently, American troops fighting in Iraq and Afghanistan updated the saying again in the form: “Kill ‘em all. Let Allah sort ‘em out.”
I think the attitude has existed since the dawn of military history.
There used to be a concept of "collateral damage"...