Ibn Saud finally consolidated control over the Nejd and the eastern coast of Arabia in 1912 with the help of an organized and well-trained army. In that year he founded the Ikhwan, a militant religious organization which was to assist in his later conquests. More broadly, he revived his dynasty's traditional alliance with the Wahhabi ulema ("scholars"). In the same year, he instituted an agrarian policy to settle the nomadic pastoralist bedouins into colonies, and to dismantle their tribal organizations in favor of allegiance to the Ikhwan. During World War I the British government attempted to cultivate favor with Ibn Saud via its political agent, Captain William Shakespear, but this was abandoned after Shakespear's death at the Battle of Jarrab. Instead, the British transferred support to Ibn Saud's rival Sharif Hussein bin Ali, leader of the Hejaz, with whom the Saudis were almost constantly at war. Despite this, the British entered into a treaty in December 1915 (the "Treaty of Darin") which made the lands of the House of Saud a British protectorate. In exchange, Ibn Saud pledged to again make war against Ibn Rashid, who was an ally of the Ottomans.
Ibn Saud did not, however, immediately make war against Ibn Rashid, despite a steady supply of weapons and cash (£5,000 Sterling per month) from the British. He argued that the payment he received was insufficient to adequately wage war against an enemy as powerful as Ibn Rashid. In 1920, however, Ibn Saud finally marched again against the Rashidis, extinguishing their dominion in 1922. The defeat of the Rashidis doubled the territory of the Ibn Saud, and he was able to negotiate a new treaty with the British at Uqair in 1922, in which Britain recognized many of his territorial gains while in exchange Ibn Saud agreed not to attempt to expand his state's borders into British protectorates on the Persian Gulf coast and in Iraq. British subsidies continued until 1924.
In 1925 the Sauds captured the holy city of Mecca from Sharif Hussein bin Ali, ending 700 years of Hashemite tutelage of the Islamic holy places. On 10 January 1926, Ibn Saud was proclaimed King of the Hejaz in the Great Mosque at Mecca. On May 20, 1927, following the defeat of Hussein, the British government signed the Treaty of Jeddah, which abolished the Darin protection agreement and recognized the independence of the Hejaz and Najd, covering much of what is today Saudi Arabia, with the Al Saud as its rulers. At this point, Ibn Saud changed his title from Sultan of Nejd to King of Nejd. Initially the two parts of his dominion (Nejd in the east and Hejaz in the west) were administered separately.