"The crusades were originally meant to redeem Europe from its violent nature, not to extend that violence. In this way, the crusades were intended to be a military pilgrimage of penance for the men who participated, a way of channeling the evil of their violence into a godly purpose. It was this idea that Bernard latched onto when he aided in the forming of the Templar order.
The duty of a knight was to kill his enemies and fight in the name of his lord. The duty of a Christian was to love his neighbor as himself, and to turn the other cheek when confronted with aggression. This basic contradiction was a conflict that the people of medieval Europe had a very difficult time resolving, be they men in arms or intellectuals.
Over the centuries, there were many attempts to justify either the way of the knight, or to condemn this manner of living as sinful and evil. When Bernard, abbot of Clairvaux (1090-1153) in the Cistercian order and noted scholar, was asked to write about the newly formed knights Templar, he went out of his way to condemn the normal life of the knightly class of his time, while exalting the idea of knights who fought for God alone. In this new order, Bernard saw a way of escaping the evils of the military life, and a worthy aim that would not only further the cause of the Church and of God, but would also serve as a way of redemption for the many sinful soldiers that would enter the order."
This blog quotes freely from "Bernard of Clairvaux and the Knights Templar: The New Knighthood as a Solution to Violence in Christianity" a Master Thesis by Boysel (2009). Illustration shows Bernard of Clairvaux preaching the 2nd Crusade at Vézelay in 1146, source Wikipedia