Anyone vaguely familiar with the early history of the Russian Revolution will recall the one or two lines in every textbook about Marshal Pilsudski’s legionaries stopping the Red Army before the gates of Warsaw in August 1920. The outcome is almost taken for granted. The Soviet forces, embroiled in a civil war of immeasurable savagery, were perhaps too weak to do much more; Poles were defending the independence so recently won in the Versailles settlement and fought with a stubborn nationalism. Some of this is true, but as Adam Zamoyski reminds us in this crisp account of an almost unknown war, the outcome was far from pre-ordained. If it is difficult to believe that the Soviets would have established an early version of the Cold War bloc had they won, it is also difficult to see who could have ejected them once they straddled Eastern Europe.