Part-2 of this video is @ http://youtu.be/qzzaypUHLXs
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see full video @ Promises and Betrayals - Middle East - History
http://youtu.be/JW2sm0iR0E8
There is no evidence to suggest that Sharif Hussein bin Ali was inclined to "Arab Nationalism" before 1916, however the rise of "Turkish Nationalism" in the Ottoman Empire, that culminated in the 1908 Young Turks revolution displeased the Hashemites and resulted in a rift between them and the new government. During World War I, Hussein initially remained allied with the Ottomans but began secret negotiations with the British on the advice of his son, Abdullah, who had served in the Ottoman parliament up to 1914 and was convinced that it was necessary to separate from the increasingly nationalistic Ottoman administration.

Starting in 1915, as indicated by letters of the British representative, Henry McMahon. The Secretary of State for War, Lord Kitchener, appealed to Hussein for assistance in the conflict on the side of the Triple Entente. Hussein demanded recognition of an Arab nation that included the Hejaz and other adjacent territories as well as approval for the proclamation of an Arab Caliphate of Islam. McMahon accepted and assured him that his assistance would be rewarded by an Arab empire encompassing the entire span between Egypt and Persia, with the exception of imperial possessions and interests in Kuwait, Aden, and the Syrian coast. But after protracted negotiations, with neither side committing to clear terms, including on key matters such as the fate of Palestine, Hussein became impatient and commenced with what would become known as The Great Arab Revolt against Ottoman control in 1916.