At the beginning of 1917, three warring empires were at breaking point. Russia was the first to collapse, triggering the Bolshevik Revolution; but by the end of 1918, both the German and Austro-Hungarian empires had also disintegrated. The fourth and final volume of Prit Buttar’s history of the Great War’s Eastern Front charts these momentous events and describes the ‘successor wars’ that followed the Armistice – the bitter struggles for national sovereignty that paved the way for the Second World War.