At the time of World War I, the British already had pretty much the rest of non-Ottoman Arabia under various forms of protectorates, and Persia too for that mat

At the time of World War I, the British already had pretty much the rest of non-Ottoman Arabia under various forms of protectorates, and Persia too for that matter--Persia being by far the most powerful country in the region, at least outside of the soon-to-be-carved-up Ottomans. During World War I, the British freaked out about the potential unrest that the Ottoman sultan (as caliph) could provoke in their Muslim lands, and as a result made multiple incompatible agreements with whatever forces would be willing to help fight against the Ottomans in the Middle East. In particular, everyone was promised Palestine if they would help in the fight. When it came time to do the actual carving, the British, in fine imperial tradition, honored none of these agreements. In the actual agreement, the British and the French carved up the Arab regions somewhat (but not entirely) in the vein of the Sykes-Picot agreement, with the French choosing for themselves a majority Christian domain in Lebanon and a majority Muslim domain in Syria. The British kept Palestine for itself, granted Hejaz independence along its original Ottoman provincial boundaries, and created independent states of Transjordan and Iraq, each to be ruled by the sons of the new Hejai king (the upgraded Sharif of Mecca).