Royal

Sir Edward Walker, the King Charles I’s Secretary for War, estimated the royal army at Second Newbury (made up of  the King’s Oxford Army and Western Army under the King’s nephew, Prince Maurice) as consisting of 5,500 foot and 4,000 horse.    The Oxford army was organised into three infantry brigades containing a total of 3,500 foot soldiers, excluding officers, under the command of colonels Thomas Blagg, George Lisle and Sir Bernard Astley and four cavalry brigades under the Earl of Cleveland, Lord Wentworth, Sir Humphry Bennet and Thomas Howard as well as some independent cavalry units; in all around 3,500 horse.  The Western Army consisted of 2,000 infantry divided into three brigades and about 500 cavalry.   

Parliament

Parliamentary forces were made up of armies commanded by the earl of Essex, the earl of Manchester and Sir William Waller as well as a brigade of London militia troops under Sir James Harrington.  These numbered around 9,300 infantry and 7,300 cavalry in total.  The size and organization of Essex’s Army can be estimated from the Exchequer papers in The National Archives.  The pay warrants for Essex’s eight regiments of foot are available for 21 October 1644, though they do not provide numbers of soldiers, only the amounts paid to the regiments for both officers and soldiers.  Based on other pay warrants where numbers of soldiers are known, Essex foot regiments are estimated to have consisted of just under 3,200 common soldiers.  Essex’s cavalry, again based on pay warrants, for his seven regiments of horse totalled a little under 2,000 men excluding officers.  The four regiments of the London militia brigade added approximately a further 2,400 infantry to the Army (the brigade was five regiments and 3,000 men strong at Reading, but one regiment was left there before it advanced to rendezvous with the rest of Parliament's armies around 19 October 1644).  Numbers for the armies under the earl of Manchester and Sir William Waller are more difficult to calculate as the pay warrants are not as complete or as comprehensive as those produced for the earl of Essex’s army. Nevertheless the work undertaken by Laurence Spring suggests that Manchester’s nine regiments of foot consisted of around 3,700 men excluding officers and his four regiments of horse about 2,700 troopers.  Waller’s army was devoid of infantry following its disaster at Cropredy Bridge in June 1644 and his eight regiments of horse perhaps numbered 2,600 troopers.  Waller also had around 400 dragoons.