 Marwan 's 737 expedition was the climax of the Arab – Khazar wars , but its actual results were meagre . Although the Arab campaigns after Ardabil may indeed have discouraged the Khazars from further warfare , any recognition of Islam or of Arab supremacy by the khagan was evidently conditional upon the presence of Arab troops deep in Khazar territory , and such presence could not be sustained for long . Furthermore , the credibility of the conversion of the khagan to Islam is disputed : al @-@ Baladhuri 's account , which probably reflects closer the original sources , suggests that it was not the khagan but a minor lord who converted to Islam and was placed in charge of the Khazars at al @-@ Lakz . The conversion of the khagan is also apparently contradicted by the fact that c . 740 the Khazar court embraced Judaism as its official faith , a decision which clearly owed a great deal to the determination of the Khazars to avoid assimilation by and emphasize their independence from the Christian Byzantine and the Muslim Arab empires . 
