With these resources, Henry erected a number of siege engines around the castle; one probable trebuchet and two mangonels were set up to the east of the castle; two mangonels were placed on the west side, to attack the keep, and one mangonel on both the north and south sides. Two siege-castles were established to observe the occupants of the castle. William was confident, however, that either his brother would return and relieve the siege, or that the pope would intervene, and held on despite the artillery attacks. The losses in the royal army began to mount; chronicler Ralph of Coggeshall suggests that seven knights, and over 200 soldiers and labourers were killed as the siege dragged on.