Self - denying Ordinance The Self - denying Ordinance was passed by the Long Parliament of England on 3 April 1645 . Under its terms all members of the Long Parliament who were also officers in the Parliamentary army or navy were to either resign their Parliamentary seat or their military commission . This ordinance was part of a set of reforms aimed at Parliament forces , which resulted in the New Model Army , which was a centralized national arm that replace parliamentary regional armies such as the Eastern Association . It was the second attempt to pass such a measure , the first bill having been moved on 9 December 1644 , had failed to pass the House of Lords . Political motivation . At the outset of the English Civil War , Parliament gave command of its main armies to members of the aristocracy . This was in accordance with well - established practices of the day , and generalships were accorded to the earls of Manchester and Essex among others . Edward Montagu , Earl of Manchester , was given charge of the Eastern Association , where Cromwell served under him as a cavalry officer . Parliament was soon hindered by dissension within this military leadership . These officers were not professional soldiers ; their experience and skill at warfare varied . More significantly , a faction of them avoided engagements with the Cavalier forces , hoping that reconciliation with King Charles I was still possible . The Earl of Manchester , perhaps the most prominent of these , expressed his pessimism for the war as follows : " If we beat the King ninety and nine times yet he is king still , and so will his posterity be after him ; but if the King beat us once , we shall be all hanged , and our posterity be made slaves " . As the war proceeded , it was clear that Essex and Manchester were at best half - hearted in pursuing the fight against the royalists , an attitude that became ever more apparent as the struggle became more radical . The growing rift between the Lords and the Commons finally came to a point of crisis when the fruits of the great victory at the battle of Marston Moor were allowed to slip away at the disappointing second battle of Newbury . It was after this that the political tensions between Cromwell and Manchester could no longer be contained by the established forms of command . Members of Parliament , notably Oliver Cromwell and Sir William Waller , saw the need for radical reform of the army . For Cromwell , this attack on Manchester ' s conduct ultimately became an attack on the Lords , most of whom held the same views as Manchester , and on the Scots , who attempted to bring Cromwell to trial as an " incendiary " . At the height of this bitter controversy , Cromwell suddenly proposed to stifle all animosities by the resignation of all officers who were members of either House . This proposal , in theory , affected himself no less than the Earls of Essex and Manchester . Terms of the ordinance . The first self - denying bill was put before Parliament on 9 December 1644 . It provided that " no member of either house shall have or execute any office or command . . . " , etc . in the armed forces . One of the exceptions was Oliver Cromwell . It passed the House of Commons on 19 December but was thrown out by the Lords on 13 January 1645 . The Lords , naturally , were reluctant to approve an ordinance that would automatically exclude nobles from military command . It also " weeded out " the " half measures men " such as Lords Fairfax and Manchester . A second version of the bill was prepared , which required resignations as above , but did not forbid re - appointment of the officers . This bill was agreed to on 3 April 1645 . Historic significance . The self - denying ordinance improved military unity by separating the quarrels in Parliament from the immediate operations of command . Leaders from the Presbyterian “ peace party " faction in Parliament resigned their military positions to retain their political powers ; Lords Manchester and Essex forfeited their generalships , as Lord Warwick did his command of the navy . Leadership of Parliament ’ s troops fell to Sir Thomas Fairfax , then a lieutenant general , who was among the few officers still eligible for the post . In practical terms , the ordinance solidified the power of Cromwell and his “ war party ” faction . Cromwell was a member of the House of Commons , so he was obligated to resign his post as well . However , the Committee of Both Kingdoms , which oversaw the war , found his talents as a soldier indispensable . His term in command was extended several times , in forty - day increments , until it was finally made permanent . While this appointment was officially as Fairfax ’ s lieutenant general , Cromwell wielded influence well beyond his rank . More broadly , this reform helped usher in Cromwell ’ s New Model Army . This reorganized force , designed for unity and efficiency , incorporated several practices recognizable in modern armies . In addition to a professional officer corps promoted on merit , it replaced the sometimes baulky local units with nationally controlled regiments , standardized training protocols , and ensured regular salary payments to the troops . This army soon turned the war in favour of Parliament , decisively beating the Royalist forces at the battle of Naseby on 14 June 1645 .