Like Armenians, Assyrians, and other Ottoman subjects, the Greeks of Trebizond and the short-lived Russian Caucasus province of Kars (which, in 1918, fell back under Ottoman control) suffered widespread massacres and what is now usually termed ethnic cleansing at the beginning of the 20th century, first by the Young Turks, and later by Kemalist forces. In both cases, the pretext was again that the Pontic Greeks and Armenians had collaborated or fought with the forces of their Russian co-religionists and "protectors" before the termination of hostilities between the two empires that followed the October Revolution. Death marches through Turkey's mountainous terrain, forced labour in the infamous "Amele Taburu" in Anatolia, and slaughter by the irregular bands of Topal Osman resulted in tens of thousands of Pontic Greeks perishing during the period from 1915 to 1922. In 1923, after hundreds of years, those remaining were expelled from Turkey to Greece as part of the population exchange between Greece and Turkey defined by the Treaty of Lausanne. In his book "Black Sea", author Neal Ascherson writes: