ed ▁off , ▁and ▁a ▁semi - per man ent ▁border ▁between ▁the ▁two ▁powers ▁was ▁established , ▁a ▁wide ▁zone , ▁un c laimed ▁by ▁either ▁By z ant ines ▁or ▁Arab s ▁and ▁virt ually ▁desert ed ▁( known ▁in ▁Arab ic ▁as ▁al - <0xE1> <0xB8> <0x8C> aw ā ḥ ī , ▁" the ▁outer ▁lands " ▁and ▁in ▁Greek ▁as ▁, ▁ta ▁ak ra , ▁" the ▁extrem ities ") ▁emer ged ▁in ▁C il icia , ▁along ▁the ▁southern ▁approaches ▁of ▁the ▁T aur us ▁and ▁Anti - T aur us ▁mountain ▁ranges , ▁leaving ▁Sy ria ▁in ▁Muslim ▁and ▁the ▁An atol ian ▁plate au ▁in ▁By z antine ▁hands . ▁Both ▁Emperor ▁Her ac lius ▁and ▁the ▁C ali ph ▁' U mar ▁( r . ▁ 6 3 4 – 6 4 4 ) ▁purs ued ▁a ▁strategy ▁of ▁destruction ▁within ▁this ▁zone , ▁trying ▁to ▁transform ▁it ▁into ▁an ▁effective ▁bar rier ▁between ▁the ▁two ▁real ms . ▁ ▁Nevertheless , ▁the ▁Um ay y ads ▁still ▁considered ▁the ▁complete ▁sub j ug ation ▁of ▁By z ant ium ▁as ▁their ▁ult imate ▁objective . ▁Their ▁thinking ▁was ▁domin ated ▁by ▁Islam ic ▁teaching , ▁which ▁placed ▁the ▁inf idel ▁By z ant ines ▁in ▁the ▁D ā r ▁al - Ḥ ar b , ▁the ▁" H ouse ▁of ▁War ", ▁which , ▁in ▁the ▁words ▁of ▁Islam ic ▁scholar ▁Hugh ▁N . ▁Kennedy , ▁" the ▁Muslim s ▁should ▁attack ▁whenever ▁possible