Great Rebellion, or English Civil War, a war fought in Great Britain, 1642–1652. In the first phase of the conflict, 1642–46, the forces of the English Parliament, aided by Scottish Presbyterians, defeated the Royalist army. In the second, 1648–52, Royalists and Presbyterian Puritans were defeated by the Independent Puritan forces of Oliver Cromwell. Charles I was beheaded and a new government, the Commonwealth, was created. The monarchy was restored in 1660, but royal authority was never again as strong as before the Great Rebellion.