The demographics of this area underwent a huge shift in the early part of the 20th century. Some Circassian, Kurdish and Chechen tribes cooperated with the Ottoman (Turkish) authorities in the Armenian and Assyrian genocides in Upper Mesopotamia, between 1914 and 1920, with further attacks on unarmed fleeing civilians conducted by local Arab militias. Many Assyrians fled to Syria during the genocide and settled mainly in Al-Jazira Province. Starting in 1926, the region saw another immigration of Kurds following the failure of the Sheikh Said rebellion against the new Republic of Turkey. While there have been Kurds in Syria for centuries, waves of Kurds fled their homes in Turkey and settled in Syria, where they were granted citizenship by the French mandate authorities. In the 1930s and 1940s, the region saw several failed autonomy movements.