The entry of the Scots into the English Civil War (1642?1651) on 19 January 1644 on the side of Parliament radically changed the balance of power in the North of England. The Royalists in the North were forced onto the defensive and besieged in York. In a bold march Prince Rupert outmanoeuvred his enemies and relieved York without a shot being fired. However, when Rupert met the allied army in battle on Marston Moor on 2 July his cavalry was defeated by Cromwell's Ironsides who then turned on the Royalist infantry. The result was a hard-fought but catastrophic defeat; the Royalist army was crushed and their forces driven from the north of England.