The development of the Knight depended on the union of technological and cultural change. The strength and stability of the stirrup opened the door for the heavily armored Knight to make shock charges into the enemy line. After the discovery of the stirrup, horses, once small and lithe, were bred with much stronger forelegs to absorb the new levels of impact. Stronger horses could carry more armor, creating a Dark Ages arms race. Unable to afford the new costs, kings loaned land to local warriors who provided for a set number of knights in return. This reciprocal relationship later developed into feudalism.