The Conquest of al-Hasa was achieved by the Saudi forces of ibn Saud with support from the Ikhwan in 1913. The Oasis of al-Hasa was conquered from an Ottoman garrison, who had controlled the area from 1871. Although Shia Islam religious community leaders negotiated a quick surrender and recognition of the Sunni Islam Saudi political authority in exchange for leniency, the Shia communities in al-Hasa and Qatif were subjected to harsh oversight and cruelty.