"History down to now has not thought out any other way of carrying mankind forward than that of setting up always the revolutionary violence of the progressive classes against the conservative violence of the outworn classes." Besigned by imperialism, attacked from within by the scum of the Tsarist officers, in the three years following October 1917 the Russian Revolution also had to counter the assaults of its enemies within the international labour movement. This book is Trotsky's reply to the renegade from Marxism, Karl Kautsky. Written in the midst of the fighting, while he was directing the campaigns of the Red Army, it lays down uncompromisingly the historical justifications of the actions of the Bolsheviks. It reamins a crucial part of the fight to bring the lessons of the October Revolution to the international working class.