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.