The focus of this work is a comparative analysis of the Bolshevik theory on the national question and the Bolshevik state-party practice in the Soviet national republics and regions. For the first purpose, the author examined all the most important works of Lenin and Stalin on the national question and all the most important documents on this issue of the highest party bodies. As for the second goal - the Bolshevik practical solution to the national problem by creating a union of “sovereign Soviet republics” in the form of the USSR, then, using the same official documents, the author tries to show the degree and nature of the “sovereignty” of the union republics in action .