After Rome's fall, some of the medieval European kingdoms that rose upon its wreckage maintained units of mounted warriors. Over time, elite individuals in the ranks of those units gained fame as knights—fighters of exceptional skill and courage, whose armor grew to cover their entire bodies and who also enjoyed high social status. Knights took an oath to serve God and their king and developed a special code of honorable behavior called chivalry, which, regrettably for their victims, they did not always follow.