 Complete the following phrase:  Unsurprisingly, the relationship between caliph and vizier remained extremely hostile: according to Usama ibn Munqidh, the two despised each other, with the Caliph conspiring to kill Ibn al-Sallar, and the latter seeking to depose the Caliph. The mutual hatred of both men was only kept in check by the grave external threats faced by the empire from the Crusader Kingdom of Jerusalem. Ibn al-Sallar entertained the notion of an alliance and joint action with the Zengid ruler of Aleppo, Nur al-Din, but this did not come to pass, as the latter was focused on capturing Damascus at the time. Nevertheless, following the sack of Farama by the Crusaders, in 11512 Ibn al-Sallar mobilized the Fatimid navy to raid Christian shipping along the coasts of the Levant from Jaffa to Tripoli, Lebanon. The fleet inflicted significant casualties and returned victorious. This success strengthened Ibn al-Sallars position domestically, but was hollow, as neither the Fatimids nor Nur al-Din followed it up; in contrast, in early 1153 the Crusaders 