Charles I besieged the Parliamentarian stronghold of Gloucester in August 1643. The city resisted until the Earl of Essex approached with a relief army, prompting the Royalists to withdraw on 5 September. Gloucester's survival denied the king control of the Severn valley and revived Parliamentarian morale.

Sermons and pamphlets celebrated Gloucester as a city delivered by providence. Its resistance became a civic legend in which steadfast townspeople, ministers and soldiers defended both true religion and parliamentary liberty.