il ' s ▁A yy ub id ▁success ors ▁re built ▁many ▁of ▁the ▁administrative ▁and ▁domestic ▁structures ▁inside ▁the ▁cit adel , ▁including ▁resid ences , ▁pal aces , ▁and ▁a ▁pool . ▁As - S ali h ▁A yy ub ▁was ▁the ▁only ▁successor ▁who ▁also ▁modified ▁the ▁def ences . ▁ ▁Possible ▁motiv ations ▁for ▁this ▁complete ▁re building ▁by ▁Al - Ad il ▁include ▁the ▁damage ▁the ▁old ▁cit adel ▁may ▁have ▁sust ained ▁from ▁earth qu akes ▁in ▁ 1 2 0 0 ▁and ▁ 1 2 0 1 ▁and ▁the ▁threat ▁that ▁other ▁A yy ub id ▁princes ▁continued ▁to ▁pose ▁toward ▁Al - Ad il . ▁The ▁most ▁likely ▁motiv ation ▁is ▁that ▁the ▁def ences ▁of ▁the ▁old ▁cit adel ▁became ▁ob sole te ▁due ▁to ▁the ▁introduction ▁in ▁the ▁ 1 2 th ▁century ▁of ▁the ▁counter weight ▁tre buch et , ▁a ▁sie ge ▁engine ▁easily ▁capable ▁of ▁reducing ▁thick ▁stone ▁walls ▁to ▁rub ble . ▁The ▁new ▁cit adel ▁introduced ▁a ▁number ▁of ▁important ▁changes ▁to ▁the ▁def ensive ▁system , ▁including ▁higher ▁and ▁th icker ▁walls , ▁a ▁wide ▁mo at ▁surrounding ▁the ▁cit adel , ▁and ▁numerous ▁closely ▁spac ed , ▁high , ▁massive ▁to wers . ▁Un like ▁the ▁older ▁to wers , ▁these ▁were ▁square ▁rather ▁than ▁round ▁in ▁design . ▁The ▁to wers ▁contained ▁platforms ▁on ▁which ▁tre buch ets ▁could ▁be ▁placed . ▁Due ▁to ▁their ▁high ▁position , ▁these ▁tre buch ets ▁could ▁out range