The Commonwealth, or Commonwealth of England, was the period from 1649 onwards when England, along later with Ireland and Scotland, was ruled as a republic following the end of the Second English Civil War and the trial and execution of Charles I. The republic's existence was initially declared through "An Act declaring England to be a Commonwealth", adopted by the Rump Parliament on 19 May 1649. Power in the early Commonwealth was vested primarily in the Parliament and a Council of State. During the period, fighting continued, particularly in Ireland and Scotland, between the parliamentary forces and those opposed to them, as part of what is now referred to as the Third English Civil War.
In 1653, after the forcible dissolution of the Rump Parliament, Oliver Cromwell was declared Lord Protector of a united "Commonwealth of England, Scotland and Ireland" under the terms of the Instrument of Government, inaugurating the period now usually known as the Protectorate. After Cromwell's death, and following a brief period of rule under his son, Richard Cromwell, the Protectorate Parliament was dissolved in 1659 and the Rump Parliament recalled, the start of a process that led ultimately to the restoration of the monarchy in 1660. The term Commonwealth is sometimes used for the whole of 1649 to 1660 – a period referred to by monarchists as the Interregnum – although for other historians, the use of the term is limited to the years prior to Cromwell’s formal assumption of power in 1653.