An exchange of letters between Henry McMahon, British High Commissioner in Egypt, and Hussein bin Ali, Sharif of Mecca and later King of Hejaz, that took place in late 1915 and early 1916. With the Arabs planning to revolt against the Ottoman Empire in the midst of World War I, the exchange promised British support to the Arabs, and British recognition of Arab independence following the war, with certain territorial reservations. Implementation of the British promises contained in the exchange was complicated by the exposure of the secret Sykes-Picot Agreement, defining British and French spheres of influence in the Middle East, as well as the publication of the Balfour Declaration, endorsing the establishment of a Jewish homeland in Palestine.