I (known as the Eastern Front). The Ottoman Empire did not join the world war until several months had passed and, as the possibility of a Caucasus Campaign come closer, in the summer of 1914, Count Illarion Ivanovich Vorontsov-Dashkov consulted with the Mayor of Tbilisi Alexandre Khatsian, the primate of Tbilisi, Bishop Mesrop, and the prominent civic leader Dr. Hakob Zavriev about the creation of Armenian volunteer detachments. The volunteer units would be made up from Armenians who were not subjects of the empire or not obliged to serve in the army. These units would be employed on the Caucasus Campaign. Many of them were living in the Caucasus and many were impatient to take up arms to liberate their homeland. During the course of the war 150,000 Armenians fought in the Russian Army. Occupation of Turkish Armenia The Ottoman authorities embarked on the genocide of their Armenian subjects as early as April 1915 following the rapid Russian advance in the Caucasus Campaign and the Siege of Van. An Armenian provisional government within the autonomous region was initially set up around Lake Van. The Armenian government in the war zone was briefly referred to as "Free Vaspurakan", and after an Ottoman advance in June 1915. With the Ottoman advance in June 1915 250,000 Armenians from Van and the neighbouring region of Alashkerd retreated to the Russian frontier. Russian Transcaucasia was flooded with refugees from the massacres. While it scored military successes against the Turks, the Russian war machine began to disintegrate on its front against Germany and in February 1917 the tsarist regime was overthrown by a revolution in Saint Petersburg. Russian Armenians greeted the new government with enthusiasm, hoping it would secure Ottoman Armenia for them. The issue of the continuation of the war was a highly contentious one amongst the political parties of the new Russia, with most favouring a "democratic peace"; but since the provinces of Ottoman Armenia were under Russian military occupation at the time of the revolution, the Armenians believed that the government would agree to defend them. To help out, the Provisional Government began replacing Russian troops, whose commitment to continued fighting was in doubt, with Armenian ones on the Caucasian front. But as 1917 went on the Provisional Government lost support among Russian soldiers and workers and much of the army melted away from Transcaucasia. Armenian Congress of Eastern Armenians The Bolshevik Revolution