In 1915, as the Russian Caucasus Army continued to advance in eastern Anatolia with the help of Armenian volunteer units from the Caucasus region of the Russian Empire, and aided by some Ottoman Armenians, the Ottoman government decided to issue the Tehcir Law, which started the deportation of the ethnic Armenians, particularly from the provinces close to the Ottoman-Russian front, resulting in what became known as the Armenian Genocide. Through forced marches and gang skirmishes, the Armenians living in eastern Anatolia were uprooted from their ancestral homelands and sent southwards to the Ottoman provinces in Syria and Mesopotamia. Estimates vary on how many Armenians perished, but scholars give figures ranging from 300,000 (per the modern Turkish state), 600,000 (per early estimates by Western researchers) to up to 1.5 million (per modern Western and Armenian scholars).