England conquered Wales during the Middle Ages. The Normans, under William the Conqueror, took the eastern and southern regions in the twelfth century. William set up barons in these border areas, or “marches”, and gave them power that exceeded that of most other barons. This bred ambitions and a sense of autonomy among the Lords Marchers that would haunt the English crown for centuries. For good or ill, these barons played pivotal roles in the rebellions and politics of the medieval period.