At the centre, there was a struggle between King Charles I and the Parliament of England over how England should be ruled. The King wanted to rule without Parliament telling him what to do. At first Parliament wanted to reduce the King's power, but later it decided that the country did not need a king. King Charles's supporters were known as the Royalists, and were nicknamed "Cavaliers". Parliament's supporters were known as the Parliamentarians, and were nicknamed "Roundheads".