Blankinship also highlights the limited gains made by the Caliphate in the Second Arab–Khazar War as disproportionate to the resources expended: Arab control was in reality limited to the lowlands and coast, and the land itself was too poor to recompense the Umayyad treasury. More importantly, the need to maintain the large garrison at Derbent further depleted the already overstretched Syro-Jaziran army, the main pillar of the Umayyad regime. Eventually, the weakening of the Syrian army through its dispersion across the various fronts of the Caliphate would be the major factor in the fall of the Umayyad dynasty during the Muslim civil wars of the 740s and the Abbasid Revolution that followed them.