Caedite eos. Novit enim Dominus qui sunt eius

"Caedite eos. Novit enim Dominus qui sunt eius." was a phrase allegedly spoken by Papal legate and Cistercian abbot Arnaud Amalric prior to the Massacre at Béziers, a massacre in the French town of Béziers that formed the first major military action of the Albigensian Crusade. A direct translation of the Latin phrase would be "Kill them. For the Lord knows those that are His own." Less formal English translations have given rise to variants such as "Kill them all; let God sort them out." Other sources give the quotation as "Necaeos omnes. Deus suos agnoset."

Background
Amalric's own version of the siege, described in his letter to Pope Innocent III in August 1209, states: While discussions were still going on with the barons about the release of those in the city who were deemed to be Catholics, the servants and other persons of low rank and unarmed attacked the city without waiting for orders from their leaders. To our amazement, crying "to arms, to arms!", within the space of two or three hours they crossed the ditches and the walls and Béziers was taken. Our men spared no one, irrespective of rank, sex or age, and put to the sword almost 20,000 people. After this great slaughter the whole city was despoiled and burnt...

About twenty years later Caesarius of Heisterbach relates this story about the massacre, When they discovered, from the admissions of some of them, that there were Catholics mingled with the heretics they said to the abbot "Sir, what shall we do, for we cannot distinguish between the faithful and the heretics." The abbot, like the others, was afraid that many, in fear of death, would pretend to be Catholics, and after their departure, would return to their heresy, and is said to have replied "Caedite eos. Novit enim Dominus qui sunt eius - Kill them all for the Lord knoweth them that are His" (2 Tim. ii. 19) and so countless number in that town were slain.

Caesarius did not state that this sentence had been actually uttered, he wrote that Amalric "was reported to have said it" (dixisse fertur in the original text). While there remains doubt that the abbot said these words there is little if any doubt that these words captured the spirit of the assault, and that the crusaders intended to kill the inhabitants of a stronghold that offered resistance. However, typically that would involve killing the men, not women and children, and not the clergy. The crusaders allowed the routiers to rampage and kill without restraint, but quickly stepped in when it came to the loot.

Meaning
The Albigensian Crusade was intended to eliminate Catharism, a Christian movement denounced by the Catholic Church as heresy. Béziers was a Cathar stronghold, but it was still home to orthodox Catholics as well. Presented with the difficulty of distinguishing them from the heretics, especially if individuals misrepresented their own beliefs, the phrase indicated that God would judge those who were killed, and accordingly "sort" them into Heaven or Hell.

The phrase has been called a misapplication of 2 Timothy 2:19, "Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are His." (KJV)

In culture
The phrase has been adopted by members of the US military in various conflicts, such as the Vietnam War, and is used as an unofficial slogan by certain units. In parts of the War on Terror, the variant "Kill them all. Let Allah sort them out." has been used.