“Lenin early learned the inevitability of this development of centrifugal national movements in Russia, and for many years stubbornly fought – most particularly against Rosa Luxemburg – for that famous paragraph 9 of the old party programme which formulated the right of nations to self-determination – that is, to complete separation as states. In this the Bolshevik Party did not by any means undertake an evangel of separation. It merely assumed an obligation to struggle implacably against every form of national oppression, including the forcible retention of this or that nationality within the boundaries of the general state. Only in this way could the Russian proletariat gradually win the confidence of the oppressed nationalities.”

https://www.marxists.org/archive/trotsky/1930/hrr/ch39.htm