INFANTRY: 7,500 fit for service
Oliver Cromwell was an extremely able and experienced commander, who had risen to prominence fighting for the English Parliament in the Civil War. Since the execution of King Charles I he had stormed through Ireland suppressing the remaining opposition. The army he brought into Scotland in 1650 was well led and well motivated. At its core were veteran campaigners, united in their determination to prevent Scotland becoming a rallying point for the royalist cause they had fought so long to defeat. The infantry were divided into pikemen and musketeers, and the cavalry were formidable armoured shock troops known as "ironsides". There was also a mixed train of artillery to support the army in action. Despite their initial confidence, the failure to bring the Scots to battle quickly led to sickness and supply shortages, reducing the army's initial strength by almost 5,000 men.
INFANTRY: Around 15,000
CAVALRY: Around 6,000
David Leslie was a professional soldier and had cut his teeth fighting in Europe before civil war broke out in Britain. When the Scots were allied with the English Parliament he had fought at Cromwell's side. Leslie had defeated the feared royalist Montrose, cementing his reputation. Leslie's army was large but mostly comprised fresh recruits. Some of his veteran officers had to be discharged because of suspected royalist sentiments, undermining the confidence and capacity of the army. Nevetheless, this was a large and capable army which had performed well in checking Cromwell's advance. As well as pikemen and musketeers recruited from right across Scotland, Leslie had a large force of cavalry. Many of these were lancers, lighter armed than their opponents but they had already proven their worth at Musselburgh and Haddington.