Battle of Naseby (1645). The Battle of Naseby was a decisive engagement of the First English Civil War, fought on 14 June 1645 between the main Royalist army of King Charles I and the Parliamentarian New Model Army, commanded by Sir Thomas Fairfax and Oliver Cromwell. It was fought near the village of Naseby in Northamptonshire. After the Royalists stormed the Parliamentarian town of Leicester on 31st May 1645, Fairfax was ordered to lift his siege of Oxford, the Royalist capital, and engage the King's main army. Eager to bring the Royalists to battle, Fairfax set off in pursuit of the Royalist army, which was heading to recover the north. The King, faced with retreating north with Fairfax close behind, or giving battle, decided to give battle, fearing a loss of morale if his army continued retreating. After hard fighting, the Parliamentarian army had effectively destroyed the Royalist force, which suffered 7,000 casualties out of 7,400 effectives. Charles lost the bulk of his veteran infantry and officers, all of his artillery and stores, his personal baggage and many arms, ensuring the Royalists would never again field an army of comparable quality. Captured in the baggage train were the King's private papers, revealing to the fullest extent his attempts to draw Irish Catholics and foreign mercenaries into the war. Publication of these papers gave Parliament an added moral cause in fighting the war to a finish. Within a year, Parliament had won the first civil war. After a disappointing performance by the Parliamentarian armies at the Second Battle of Newbury at the end of the 1644 campaign season, where they failed to inflict a decisive defeat on the Royalists, Parliament reformed its armies into the New Model Army, which was not subject to interference from local associations of counties. At the same time, Oliver Cromwell worked to push the Self-denying Ordinance through Parliament. This legislation, which forbade members of the Lords or Commons from holding command in the army, was ostensibly intended to improve unity among the bickering Parliamentarian commanders, by preventing conflicts of interest. In practice, it was engineered to remove hereditary peers, many of whom were not hardline anti-Royalists, from their commands as, unlike elected Members of Parliament, they could not resign their political seats to take a commission. At the beginning of 1645, most of King Charles's advisers urged him to attack the New Model Army while it was still forming. However, Prince Rupert of the Rhine, who had recently been appointed General of the Army, and therefore the King's chief military adviser, proposed instead to march north to recover the North of England and join forces with the Royalists in Scotland under the Marquess of Montrose. This course was adopted, even though the King's army had to be weakened by leaving a detachment under Lord Goring, the Lieutenant General of Horse, to hold the West Country and maintain the Siege of Taunton, in Somerset. At the same time, after the New Model Army had abandoned its attempt to relieve Taunton, Parliament's Committee of Both Kingdoms had directed Fairfax, its commander, to besiege Oxford, the King's wartime capital. Initially, Charles welcomed this move, as Fairfax would be unable to interfere with his move north. Then at the end of May he was told that Oxford was short of provisions and could not hold out long. To distract Fairfax, the Royalists stormed the Parliamentarian garrison at Leicester on 31 May. Having done so, Prince Rupert and the King's council reversed their former decision and marched south to relieve Oxford.