 Most provinces of the Caliphate continued to recognize Ibn al-Zubayr, while the Qaysi tribes regrouped under Zufar ibn al-Harith al-Kilabi and resisted Umayyad rule in the Jazira from al-Qarqisiya, a Euphrates river fortress strategically located at the crossroads of Syria and Iraq.Re-establishing Umayyad rule across the Caliphate was the major priority of Abd al-Malik.His initial focus was the reconquest of Iraq, the Caliphate's wealthiest province.