The great religious orders of Christianity - the Benedictines, the Dominicans, the Franciscans and the Jesuits - are well known for their monasteries, their learning and their missions around the world. But in the Middle Ages, to some extent surviving to this day, there was another kind of religious order, one whose members' profession was to bear arms in defence of Christendom. From humble beginnings in the early 12th century, caring for the sick in the Holy Land and protecting pilgrims, the military religious orders spread out across Europe. Not only did they fight for the holy places, they helped push back Islam in Spain and what is now Portugal, and spread Christianity to the lands across the Baltic, then still pagan. The Knights of St John, the Knights Templar, the Knights of Santiago and of Calatrava, the Teutonic Knights and others played a fearsome, sometimes brutal and often neglected role in the history of Christianity. The wars, which they fought in the name of Christ, helped shape the world as we know it.