The Commonwealth was the political structure during the period from 1649 to 1660 when England and Wales, later along with Ireland and Scotland, were governed as a republic after the end of the Second English Civil War and the trial and execution of Charles I. The republic's existence was 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, in the Cromwellian conquest of Ireland and the Anglo-Scottish war of 1650–1652.

The Second English Civil War took place between February and August 1648 in England and Wales. It forms part of the series of conflicts known collectively as the 1639–1653 Wars of the Three Kingdoms, which include the 1641–1653 Irish Confederate Wars, the 1639–1640 Bishops' Wars, and the 1649–1653 Cromwellian conquest of Ireland.