The Umayyads' conquests meant that most of the caliphate's population was non-Arab. Many of them converted to Islam, but were treated as second-class Muslims by the Arabs and still had to pay the burdensome "jizya" tax. This led to widespread discontent and hostility towards the Umayyads. The Abbasid family exploited the discontent and organized a rebellion, overthrowing the Umayyads in 750. The Abbasids, who had their power base in Persia, moved the caliphate's capital to Baghdad in 762. This change meant that Palestine lost its central position and became a province in the caliphate's periphery whose problems weren't tended to very carefully. Though it did not cause a decline in the region, it ended the Umayyads' extravagant investments in Palestine. The prestige of the tribes in Syria, including Palestine, many of whom had supported the Umayyads also diminished and they no longer influenced the caliphate's political affairs - only its rebellions.