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
Prince Rupert of the Rhine ships and cargoes. This underlined a major problem for the Royalists—the cost of maintaining the new fleet was well beyond their means. Discipline continued to deteriorate and Rupert had to intervene personally several times, including defusing one group of mutinous sailors by suddenly dangling the ringleader over the side of his vessel and threatening to drop him into the sea. Most of the fleet finally switched sides once more, returning to England in late 1648. Then, following a degree of reconciliation with Charles, Rupert obtained command of the Royalist fleet himself. The intention was to restore Royalist finances by using