The Battle of Naseby, a decisive engagement of the English Civil War, was fought between the Royalist army of King Charles I and the Parliamentarian New Model Army.
The New Model Army was formed as a result of concerns over the effectiveness of the existing Parliamentarian army that was based on local volunteers, many of whom were reluctant to fight away from home. The new army would be made up of full-time professional soldiers whose loyalty would be national rather than regional. The introduction of the Self-denying Ordinance further strengthened the new force, since it resulted in a more effective military leadership.
The New Model Army, under the command of Sir Thomas Fairfax, was besieging the King’s former capital in Oxford when news arrived that the Royalist army had captured the Parliamentarian town of Leicester. Fairfax abandoned the siege on Oxford and marched north to engage the Royalists, whom he found on the border between Northamptonshire and Leicestershire. Fairfax’s army was joined by Oliver Cromwell’s cavalry on 13 June. Faced with the choice of either fighting or retreating, the King accepted battle.
Fairfax had positioned the Parliamentarian army on a ridge, but was persuaded by Cromwell to move it to a weaker position to encourage the Royalists to attack. Prince Rupert of the Rhine soon broke through the Parliamentary left flank, but rode on to pursue fleeing Parliamentarians rather than turn and outflank the infantry. This weakened the Royalists, and Cromwell’s cavalry were able to break the remaining cavalry before turning against the infantry in the centre. Before long the Royalists began to surrender, while Charles fled. The Royalist army was virtually destroyed in the battle, with around 6,000 of its 8,000 men either killed or captured.