During World War I, the Armenians living in the Ottoman Empire were systematically exterminated by the government in the Armenian Genocide. According to some estimates, from 1894 to 1923, about 1,500,000—2,000,000 Armenians were killed by the Ottoman Empire. After the decision to exterminate the Armenians was taken by the Ottoman Ministry of Interior and first implemented with the Directive 8682 on February 25, 1915, tens of thousands of Russian Armenians joined the Russian army as Armenian volunteer units with a Russian promise for autonomy. By 1917, Russia controlled many Armenian-populated areas of the Ottoman Empire. After the October Revolution, however, the Russian troops retreated and left the Armenians irregulars one on one with the Turks. The Armenian National Council proclaimed the Republic of Armenia on May 28, 1918, thus establishing an Armenian state in the Armenian-populated parts of the Southern Caucasus.