Hereward was then joined by a small army led by Morcar, the Saxon former Earl of Northumbria who had been ousted by William. William sent an army to deal with the rebels. In 1071, Hereward and Morcar were forced to retreat to their stronghold and made a desperate stand on the Isle of Ely against the Conqueror's rule. Both the "Gesta Herewardi" and the "Liber Eliensis" claim that the Normans made a frontal assault, aided by a huge, mile-long timber causeway, but that this sank under the weight of armour and horses. The Normans then tried to intimidate the English with a witch, who cursed them from a wooden tower, but Hereward managed to set a fire that toppled the tower with the witch in it. The "Gesta" includes other fantastical tales about Hereward's prowess, including disguising himself as a potter to spy on the king and escaping from captivity.