What was the improvements of the motte and bailey castle?

Motte and Bailey castles were replaced by shell keeps and square towers. They were also replaced by concentric castles. The concentric castles were originally Motte and Bailey castles, but only some of the Motte and Baileys got to become them. Some of the first Motte and Bailey castles to be turned into concentric castles are Rochester castle and Warwick castle. They were cool