In 1916, with the encouragement and support of Britain and France (which were fighting the Ottomans in the World War I), the sharif of Mecca, Hussein bin Ali, led a pan-Arab revolt against the Ottoman Empire with the aim of securing Arab independence and creating a single unified Arab state spanning the Arab territories from Aleppo in Syria to Aden in Yemen. The Arab army comprised bedouin and others from across the peninsula, but not the Al Saud and their allied tribes who did not participate in the revolt partly because of a long-standing rivalry with the Sharifs of Mecca and partly because their priority was to defeat the Al Rashid for control of the interior. Nevertheless, the revolt played a part in the Middle-Eastern Front and tied down thousands of Ottoman troops thereby contributing to the Ottomans' World War I defeat in 1918.