From the October Revolution, French diplomats and military officers posted in Russia tried to understand the new political situation and to deal with a Bolshevik power promoting “peace without annexation or compensation”. But far from being a rupture, the sequence between November 1917 and Summer 1918 was full of military cooperation projects and alliance hypotheses between the French and the Bolsheviks. The French, their allies, and the Bolsheviks didn’t renounce until very late the idea of military cooperation, or even an alliance against Germany. It takes a series of diplomatic and military crises for the rupture to be consummated and for the Bolsheviks to be considered as enemies.