▁part ▁of ▁I bn ▁al - As ht ar ' s ▁forces ▁and ▁his ▁lieutenant ▁command ers ▁were ▁also ▁Arab s . ▁ ▁Battle ▁ ▁In ▁early ▁August ▁ 6 8 6 , ▁the ▁entire ▁body ▁of ▁I bn ▁al - As ht ar ' s ▁forces ▁march ed ▁north ▁toward ▁the ▁Z ab ▁River ▁to ▁block ▁the ▁Um ay y ad ▁army ' s ▁advance ▁into ▁Ira q . ▁Without ▁div iding ▁his ▁caval ry ▁and ▁inf antry , ▁I bn ▁al - As ht ar ▁continued ▁his ▁north ward ▁march ▁near ▁the ▁Um ay y ads ' ▁camp ▁and ▁drew ▁in ▁the ▁forces ▁of ▁Hum ay d ▁ibn ▁Hur ay th ▁al - K al bi , ▁one ▁of ▁U bay d ▁Al lah ' s ▁command ers . ▁I bn ▁al - As ht ar ▁then ▁dispatch ed ▁his ▁advance ▁forces ▁under ▁T uf ay l ▁ibn ▁La q it ▁to ▁capture ▁the ▁village ▁of ▁Bar ' ita , ▁about ▁ ▁east ▁of ▁Mos ul , ▁near ▁the ▁banks ▁of ▁the ▁Kh az ir ▁River , ▁a ▁trib ut ary ▁of ▁the ▁Z ab . ▁They ▁enc amp ed ▁at ▁Bar ' ita ▁while ▁U bay d ▁Al lah ▁and ▁his ▁troops ▁advanced ▁and ▁camp ed ▁nearby . ▁That ▁night , ▁the ▁commander ▁of ▁U bay d ▁Al lah ' s ▁left ▁wing , ▁Um ay r ▁ibn ▁al - Hub ab ▁al - S ul ami , ▁secret ly ▁met ▁and ▁defect ed ▁to ▁I bn ▁al - As