Trilogy in which people have reverted to the barbarian ways, with scientists that overlook them

There has been a nuclear war. There are now two sets of people: the barbarians and the scientists. The barbarians are distinguised by the type of weapons they are masters of, the rope/sword/short sticks etc. In the barbarian culture, they fight in a circle to sort out disagreements and arguments.

In one of the later books they are assaulting a mountain containing the scientists.

This is all I can remember.