In 1651 the parliamentarians finally won the Third English Civil War thanks to the support of Scotland and, above all, due to the military leadership of Oliver Cromwell, who created the military units that would serve as the basis for the New Model Army. With the support of these new regiments, Cromwell purged the Parliament of all opposition members. The Rump Parliament took to judgment to Charles I that was executed the 30 of January of 1649 after Second English Civil War; abolished the monarchy and the House of Lords and established a regime called Protectorate or Commonwealth in England that united monarchical and parliamentary aspects. A new Council of State was created that depended on the Army and, faced with the scarce legitimacy of the Rump Parliament, Cromwell became the owner of the situation.
Between 1649 and 1651 he subjected Ireland and Scotland, who joined the Commonwealth. In 1653 he dissolved the Rump Parliament, tired of his opposition. Following the experiment of the Barebone Parliament, which was dissolved in December 1653, a text adopted by the State Council and supported by the New Army (known as the Instrument of Government), the only attempt in the British history of a written constitution, entrusted the power to Cromwell with the title of Lord Protector of the Republic of England, Scotland and Ireland. Cromwell accepted a second chamber in Parliament and the right to appoint his successor but rejected the title of king.