sentences:  The Royalist artillery proved inadequate for the task of siege work and, faced with a shortage of ammunition, the besiegers attempted to breach the city walls by mining.With Royalist miners about to reach the city's east gate and the defenders critically low on gunpowder, a Parliamentarian army led by the Earl of Essex arrived and forced Charles to lift the siege.Following the Royalist defeat at the Battle of Edgehill in October 1642, King Charles I's control of the south was limited to Cornwall, Wales and the Marches, and a pocket of the Thames Valley around Oxford, where he based his wartime capital.