Having already allied with his father, the Scots' acceptance of Charles II as king in 1649 caused deep suspicion in England. In July 1650, Oliver Cromwell led a powerful force across the Scottish border to remove the problem. For six weeks Cromwell waged a frustrating campaign against a Scots enemy that refused to meet him in battle. By the beginning of September Cromwell's army, poorly supplied, exhausted and ravaged by sickness, was apparently trapped at Dunbar by a powerful Scots army. On 3 September he won his greatest military victory just outside the town, but in this book Stuart Reid suggests that his triumph may in fact have begun as a breakout attempt.