Ibn al-Zubayr established himself in Mecca where he rallied opposition to Yazid (), before proclaiming himself caliph in the wake of Yazid's death in 683, marking the beginning of the Second Muslim Civil War. Meanwhile, Yazid's son and successor died weeks into his reign, precipitating the collapse of Umayyad authority across the Caliphate, most of whose provinces subsequently accepted the suzerainty of Ibn al-Zubayr. Though widely recognized as caliph, his authority was largely nominal outside of the Hejaz. By 685, the Umayyad Caliphate had been reconstituted under Marwan I in Syria and Egypt, while Zubayrid authority was being challenged in Iraq and Arabia by pro-Alid and Kharijite forces. Ibn al-Zubayr's brother Mus'ab reasserted Ibn al-Zubayr's suzerainty in Iraq by 687, but was defeated and killed by Marwan's successor Abd al-Malik in 691. The Umayyad commander al-Hajjaj ibn Yusuf proceeded to besiege Ibn al-Zubayr in his Meccan stronghold, where he was ultimately slain in 692.