In this vivid article, the major historian of Stalinism J. Baberowski endeavours to show to which extent the transformation of the Russian Empire into the “nations’ state”, and of these nations into elements of structuring of the political space of the former empire reveals the very nature of the Bolshevik experiment in the early decades of the Soviet period. He notably shows how the central power continuously maintained its project of full nationalisation of socialism, notably through the brutal promotion of indigenous élites totally loyal to the regime, blind submission being the condition for privileges. The article also casts light on the dilemma without prospects that was faced from the late 1920s onwards by numerous national party leaders: Whilst proclaiming the necessity of autonomy, the Bolsheviks were destroying everywhere the traditions that could have supported it. The short narrative is concluded by an evocation of the ethnic cleansings and deportations from frontier regions entailed by the identification of “dangerous” national groups in 1933-6 (against the Kazakhs, Koreans, Kurds, Finns, and Poles) and during WWII (Crimean Tatars, Kalmyks, Baltic peoples, Ukrainians. . .), and of the new recourse to the stigmatisation of individual ethnic groups in the late 1940s, in a period of growing confrontation with the West.