 Complete the following phrase:  At the same time, the Caliph sought to bolster Fatimid credentials in the eyes of the Muslim world by once again taking up the mantle of champions of the against the Crusader Kingdom of Jerusalem, as had been the case under al-Afdal. Taking advantage of the revolt of Hugh II of Jaffa against King Fulk of Jerusalem , after a long hiatus caused by the loss of Tyre in 1124, the Fatimids resumed their attacks on the Crusader territories from their stronghold at Ascalon. As a result, Fulk was forced to construct a series of new castlesChastel Arnoul 1133, Beth Gibelin 1137, Ibelin 1141, and Blanchegarde 1142to protect the JaffaJerusalem road and provide security for Western settlers. These fortresses shifted the balance in the Crusaders favour, as they forced the Fatimid garrison of Ascalon into a defensive stance. With the fortification of Gaza in 1150, Ascalon was entirely cut off by land, paving the way for 