On 6 December 1648, the New Model Army carried out a decisive military intervention in parliamentary politics known as Pride's Purge. Led by Colonel Thomas Pride, soldiers acting under the orders of the army leadership stationed themselves at the entrance to the House of Commons. They forcibly prevented members of Parliament who were deemed sympathetic to further negotiations with King Charles I from entering the chamber.

This operation was a direct response to the parliamentary vote on 5 December, in which a majority of members had declared the King's concessions sufficient to form a basis for a treaty. The army, frustrated by what they perceived as a betrayal of their cause and a threat to the security of the nation, took control of the legislature to ensure their political objectives were met. The purge resulted in the arrest or exclusion of approximately 140 members of Parliament.

The aftermath of the purge left behind a significantly reduced assembly, which became known as the Rump Parliament. With the political opposition removed, this body was composed entirely of members who were prepared to support the army's radical agenda. This shift in power fundamentally altered the course of the English Civil War and effectively ended the possibility of a peaceful settlement with the monarchy.

The Rump Parliament quickly moved to consolidate its authority and facilitate the legal proceedings against the monarch. The key consequences of this event included:

• The removal of MPs who opposed the army's political plans.
• The establishment of the Rump Parliament as the sole legislative authority.
• The creation of the necessary conditions for the trial of King Charles I.
• A significant shift towards the eventual abolition of the monarchy.

By eliminating those who favoured reconciliation, the army ensured that the trial and subsequent execution of the King could proceed without parliamentary interference. Pride's Purge stands as a landmark moment in Stuart Britain, illustrating the extent to which military force had come to dominate the political landscape during this turbulent period of history.