bin Bajad Al-Otaibi and Faisal al-Duwaish. By 1906, Abdulaziz had driven the Al Rashid out of Najd, and the Ottomans recognized him as their client in Najd. His next major acquisition was Al-Hasa, which he took from the Ottomans in 1913, bringing him control of the Persian Gulf coast and what would become Saudi Arabia's vast oil reserves. He avoided involvement in the Arab Revolt, having acknowledged Ottoman suzerainty in 1914, and instead continued his struggle with the Al Rashid in northern Arabia. In 1920, the Ikhwan's attention turned to the southwest, when they seized Asir, the region between the Hejaz and Yemen. In the following year, Abdul-Aziz finally defeated the Al Rashid and annexed all of northern Arabia. Prior to 1923, Abdulaziz had not risked invading the Hejaz because Hussein bin Ali, King of the Hejaz, was supported by Britain. However, in that year, the British withdrew their support. At a conference in Riyadh in July 1924, complaints were stated against the Hejaz: principally, that pilgrimage from Najd was prevented. The Hejaz boycotted the implementation of certain public policy in contravention of shari'a. Ikhwan units were massed on a large scale for the first time, and under Khalid bin Lu'ayy and Sultan bin Bajad, rapidly advanced on Mecca, laying waste symbols of "heathen" practices. The Ikhwan completed their conquest of the Hejaz by the end of 1925. On 10 January 1926, Abdulaziz declared himself King of the Hejaz and on 27 January 1927, he took the title King of Najd (his previous title was Sultan). The use of the Ikhwan to effect the conquest had important consequences for the Hejaz: the old cosmopolitan society was uprooted, and a version of Wahhabi culture was imposed as a new compulsory social order. By the Treaty of Jeddah, signed on 20 May 1927, the United Kingdom recognized the independence of Abdul-Aziz's realm (then known as the Kingdom of Hejaz and Najd). After the conquest of the Hejaz, Ikhwan leaders wanted to continue the expansion of the Wahhabist realm into the British protectorates of Transjordan, Mandatory Iraq, and Kuwait. Abdul-Aziz, however, refused to agree to this, recognizing the danger of a direct conflict with the British. The Ikhwan therefore revolted but were defeated in the Battle of Sabilla in 1929, and the Ikhwan leadership were massacred. In 1932, the two kingdoms of the Hejaz and Najd were united as the "Kingdom of Saudi