 This prompted Maslama to take over personally the direction of the Khazar front in 727 , where now he was faced , for the first time , by the khagan himself , as both sides escalated the conflict . Maslama , probably reinforced with more Syrian and Jaziran troops , took the offensive . He recovered the Darial Pass , apparently lost in the period since al @-@ Jarrah 's expedition in 724 , and pushed on into Khazar territory , campaigning there until the onset of winter forced him to return to Adharbayjan . What he achieved in this expedition is unclear , but in the next year , when he repeated his invasion , it ended in what K.Y. Blankinship calls a " near disaster " . Arab sources report that the Arab troops fought for thirty or even forty days in the mud , under continuous rainfall , before scoring a victory against the khagan on 17 September 728 . How great that victory was , however , is open to question , because on his return Maslama was ambushed by the Khazars , whereupon the Arabs simply abandoned their baggage train and fled headlong through the Darial Pass to safety . In the aftermath of this campaign , Maslama was replaced yet again by al @-@ Jarrah al @-@ Hakami . For all his energy , Maslama 's campaigning failed to produce the desired results : by 729 , the Arabs had lost control of northeastern Transcaucasia and been thrust once more into the defensive , with al @-@ Jarrah again having to defend Azerbaijan against a Khazar invasion . 
