William built castles
to try and control areas where he
faced resistance. However William could not be everywhere at once.
As reward for helping his invasion,
William gave castles and nearby lands to
his Norman barons. This
helped William in two ways.
This was the feudal
system - giving land in return for service. The barons
owned the land, but in return they had to provide services for William such as
supplying knights to fight in his army.
The Feudal System