Cromwell was at the head of the Parliamentarians who waged war on Charles I of England in the 1640s. After Charles's execution in 1649, Cromwell became the leader of the republican Protectorate, which ruled England until 1660. After his death, Cromwell's son, Richard, succeeded him. But in 1660, the Protectorate had failed, and Charles I's son, Charles II, returned to England to assume his throne.