the campaign. The government instituted a commission to purge the army of anyone suspected of having supported the Engagement, as well as other men considered sinful or undesirable. This was opposed, unsuccessfully, by much of the Scottish nobility and the experienced military leaders, including Leslie. This purge removed many experienced officers and the bulk of the army was composed of raw recruits with little training or experience. Leslie prepared a defensive line of earthworks between Edinburgh and Leith, and employed a scorched earth policy between that line and the Borders. He then allowed Cromwell to advance unopposed. Lack of supplies and the hostility of the local people towards the English invaders, forced Cromwell to rely on a seaborne supply chain and he captured the ports of Dunbar and Musselburgh in order to facilitate this. Operations were hampered by persistent bad weather and the adverse conditions and a shortage of food caused much sickness in the English army, substantially reducing its strength. Cromwell attempted to bring the Scots to battle at Edinburgh. He advanced on Leslie's lines on 29 July, capturing Arthur's Seat and bombarding Leith from Salisbury Crags. Cromwell was not able to draw Leslie out and the English retired for the night to Musselburgh; their rest was disturbed by a party of Scottish cavalry raiding their camp in the early hours. Cromwell's attack coincided with a visit by Charles II to the Scottish army, where he was warmly received. Members of the Covenanter government, concerned that their Godly war would be corrupted by feelings of personal loyalty to the King, asked Charles II to leave. They then ordered a new purge, which was quickly enacted in early August, removing 80 officers and 4,000 of Leslie's men, damaging morale as well as weakening the army's strength. Throughout August Cromwell continued to try to draw the Scots out from their defences so as to enable a set piece battle. Leslie resisted, ignoring pressure from the secular and religious Scottish hierarchy to attack Cromwell's weakened army; he reasoned that the persistent bad weather, the difficult English supply situation and the dysentery and fever that had broken out in the English camp would force Cromwell to withdraw back into England before winter set in. On 31 August Cromwell did withdraw; the English army reached Dunbar on 1 September, having taken two days to march the from Musselburgh, harassed day and night by the