It is not well-known that there existed in the 12th c. an exclusively female military order of knights in Catalonia, the Order of the Hatchet. These women successfully defended their town from an attack by Moors in 1149. In recognition of their feat, the Order of the Hatchet was created. They never saw combat after that battle, but they were never forgotten, either. The men of the town had been called away to fight, and it was left to the women to hold the town, and hold it they did.
You can read more about these and other fighting women from the Middle Ages here.