Oliver Cromwell with Sir Thomas Fairfax in command and Cromwell as Lieutenant-General of cavalry and second-in-command. At the critical Battle of Naseby in June 1645, the New Model Army smashed the King's major army. Cromwell led his wing with great success at Naseby, again routing the Royalist cavalry. At the Battle of Langport on 10 July, Cromwell participated in the defeat of the last sizeable Royalist field army. Naseby and Langport effectively ended the King's hopes of victory, and the subsequent Parliamentarian campaigns involved taking the remaining fortified Royalist positions in the west of England. In October 1645, Cromwell besieged and took
History of the Puritans under King Charles I that Parliament create a new army that would be deployable anywhere in the kingdom and not tied to a particular locality. After the Second Battle of Newbury of 27 October 1644, where parliamentary forces greatly outnumbered royalist forces and yet parliamentary forces were barely able to defeat the royalist forces, Cromwell redoubled his arguments in favor of creating a new army. At this point, most of the leaders in the parliamentary army were Presbyterians who supported the Presbyterians at the Westminster Assembly. Cromwell, however, had also been following the goings-on of the Westminster Assembly and he sided with the Independents.