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.
References
Conquest of al-Hasa (1913) Wikipedia(Text) CC BY-SA