The Norman barons had to watch out, because someone might want to kill them and grab their land.
They knew all about rough-and-ready castle building. And they had plenty of peasants to get the job done.
Because they had to be built quickly, early castles were nothing like the ones that eventually got built and that we see today. In some ways they were like hill forts, except that they were much smaller and the 'hills', really mounds, were built by heaping the soil from circular ditches.
