On 19 May 1649, the Rump Parliament formally declared England to be a Commonwealth. This landmark constitutional shift followed the execution of King Charles I earlier that year, marking the official abolition of both the monarchy and the House of Lords. By establishing England as a republic, the government sought to dismantle the traditional structures of royal authority and replace them with a system rooted in the sovereignty of the people, as represented by the House of Commons.

The declaration initiated a transformative and experimental period in British history, during which the nation sought to define itself without a sovereign ruler. Governance was primarily directed by Parliament, though the influence of the New Model Army remained a critical factor in maintaining stability and shaping policy. This era was defined by a commitment to republican ideals, reflecting the radical political shifts that had emerged from the turmoil of the Civil Wars.

The establishment of the Commonwealth brought about several fundamental changes to the English state:

• The formal abolition of the monarchy and the House of Lords.
• The transition of England into a republic governed by the Rump Parliament.
• The implementation of new political structures shaped by republican ideology.
• The significant involvement of the military in the administration of the state.

This period of republican rule represented a radical departure from centuries of monarchical tradition. Throughout this time, the new government faced the immense challenge of legitimising its authority while navigating the complex social and political divisions left in the wake of the conflict. The Commonwealth experiment would continue to evolve, reflecting the ongoing struggle to reconcile the ideals of the revolution with the practical realities of governing a fractured nation.