Russian President Vladimir Putin, in a speech to the Russian nation yesterday, claimed that "Ukraine was created by Lenin." The truth is that the October Revolution had the great merit of liberating the nationalities that had been oppressed by Tsarist Russia, which Lenin called a "prison of the nations", and denied all rights to ethnic minorities. We present this letter from Lenin, written in 1919, which develops in a few pages the position of Marxism on the question of nationalities. Let Lenin speak!