Chivalry:
Knights believed in the code of chivalry. They promised to defend the weak, be courteous to all women, be loyal to their king, and serve God at all times. Knights were expected to be humble before others, especially their superiors. They were also expected to not "talk too much". In other words, they shouldn't boast. The code of chivalry demanded that a knight give mercy to a vanquished enemy. However, the very fact that knights were trained as men of war belied this code. Even though they came from rich families, many knights were not their families' firstborn. They did not receive an inheritance. Thus they were little more than mercenaries. They plundered villages or cities that they captured, often defiling and destroying churches and other property. Also the code of chivalry did not extend to the peasants. The "weak" was widely interpreted as "noble women and children". They were often brutal to common folk. They could sometimes even rape young peasant women without fear of reprisal, all because they were part of the upper class.