 In 1244 – 1245 , as @-@ Salih Ayyub had seized the area approximate to the modern @-@ day West Bank from an @-@ Nasir Dawud ; he gained possession of Jerusalem , then marched on to take Damascus , which fell with relative ease in October 1245 . Shortly afterward , Sayf al @-@ Din Ali surrendered his exposed principality of Ajlun and its fortress to as @-@ Salih Ayyub . The rupture of the alliance between the <unk> and as @-@ Salih Ayyub ended with the virtual destruction of the former by al @-@ Mansur Ibrahim , the Ayyubid emir of Homs , in October 1246 . With the <unk> defeat , as @-@ Salih Ayyub was able to complete the conquest of southern Syria . His general Fakhr ad @-@ Din went on to subdue an @-@ Nasir Dawud 's territories . He sacked the lower town of Karak , then besieged its fortress . A stalemate followed with neither an @-@ Nasir Dawud or Fakhr ad @-@ Din strong enough to dislodge the other 's forces . A settlement was eventually reached whereby an @-@ Nasir Dawud would retain the fortress , but cede the remainder of his principality to as @-@ Salih Ayyub . Having settled the situation in Palestine and Transjordan , Fakhr ad @-@ Din moved north and marched to Bosra , the last place still held by Ismail . During the siege , Fakhr ad @-@ Din fell ill , but his commanders continued the assault against the city , which fell in December 1246 . 
