Knights Templar, ~1147-1312
The Templars, officially endorsed by the Catholic Church around 1129, were one of the most wealthy and powerful of the Western Christian military orders. They were among the most prominent actors of the Christian finance and most skilled fighting units of the Crusades.
The banner of the Templars, called Baucenant, was originally vertical divided black over white. The red cross was most probably added to their robes, and presumably also their banner, at the launch of the Second Crusade in 1147. The red cross was a symbol of martyrdom. There was a cardinal rule that the warriors of the Order should never surrender unless the Templar flag had fallen.
Under pressure from King Philip of France, who was deeply in debt to the Templars, Pope Clement V disbanded the Order in 1312.