Pride's Purge was a military coup by Fairfax's army, organized by Commissary-General Ireton and executed on 6–7 December 1648 by Colonel Thomas Pride. Its purpose was to prevent the conclusion of the so-called treaty of Newport between the Long Parliament and Charles I, whom it would have reinstated on terms that the army considered unsafe and unjust. Ireton had intended to dissolve the Parliament, but was persuaded by friendly members to purge it instead, upon their promise that it would soon dissolve itself. Pride prevented 231 known supporters of the treaty from entering the House, and imprisoned 45 of them. What was left became known as the Rump.

Austin Woolrych

Pride's Purge the exclusion or arrest of about 140 members of parliament likely to vote against a trial of the captive Charles I by soldiers under the command of Colonel Thomas Pride (d.1658) in December 1648. Following the purge, the remaining members, known as the Rump Parliament, voted for the trial which resulted in Charles's execution.