The battle of Marston Moor. With the arrival of Prince Rupert, the Parliamentarian forces led by generals Leven, Fairfax and Manchester abandoned the siege of York and headed south. Rupert followed and attacked the rear of the column forcing the fleeing army to stop. The Parliamentarians held the higher and tactically better position on Long Marston Moor. The Duke of Newcastle and his Royalist men joined Prince Rupert to create an army of around eighteen thousand men while the Parliamentarians had a force of around twenty eight thousand men and had better artillery. Late in the day the fighting began with an attack by Leven and Fairfax in the centre. The attack did not go well for the Parliamentarians and Leven and Fairfax left the battlefield. Whan all seemed lost a cavalry unit commanded by Oliver Cromwell on the left of the field attacked the Royalists and gained the upper hand. The Royalists were defeated leaving some three to four thousand of their men dead.

Charles I met Parliamentary forces led by the Earl of Manchester and William Waller at Newbury. A disjointed attack by Manchester and Waller on different fronts failed to defeat the Royalist army but it was enough to leave Charles' position in peril so the King retreated and during the night his army was able to evade Manchester's outposts and escape towards Wallingford.

Charles I returned to Donnington Castle to get the guns he had left there. A battle could have been fought, one that the King was willing to take part it, but Manchester and the committee of generals declined because their forces were not in a fit state.

Parliament wanted a report into the failings of the army against King Charles I. At first the Earl of Manchester was blamed for his lack of commitment in the field but, to prevent a serious split in the country, Cromwell put forward a suggestion to change how the army was controlled. Cromwell admitted that being a commander was not easy and he himself had made mistakes on the battlefield. Cromwell's suggestion was that no member of the Commons or Lords should control an army. This would mean Manchester and the other generals would have to resign. It meant Cromwell himself would have to do so as well. Cromwell suggested that the army should reorganised.