From the caliphate's north-western African bases, a series of raids on coastal areas of the Visigothic Kingdom paved the way to the permanent occupation of most of Iberia by the Umayyads (starting in 711), and on into south-eastern Gaul (last stronghold at Narbonne in 759). Hisham's reign witnessed the end of expansion in the west, following the defeat of the Arab army by the Franks at the Battle of Tours in 732. In 739 a major Berber Revolt broke out in North Africa, which was subdued only with difficulty, but it was followed by the collapse of Umayyad authority in al-Andalus. In India the Arab armies were defeated by the south Indian Chalukya dynasty and by the north Indian Pratiharas Dynasty in the 8th century and the Arabs were driven out of India. In the Caucasus, the confrontation with the Khazars peaked under Hisham: the Arabs established Derbent as a major military base and launched several invasions of the northern Caucasus, but failed to subdue the nomadic Khazars. The conflict was arduous and bloody, and the Arab army even suffered a major defeat at the Battle of Marj Ardabil in 730. Marwan ibn Muhammad, the future Marwan II, finally ended the war in 737 with a massive invasion that is reported to have reached as far as the Volga, but the Khazars remained unsubdued.