Goal. To demonstrate the history of genocide, recall the first legal definitions of this extreme, radical, anti-human phenomenon, highlight the origins of the UN Genocide Convention, and present one's own perspective on why this Convention was largely unapplied for a long time, despite the obvious facts of genocide during World War II against the peoples of the Soviet Union, as those most affected by the aggression of Nazi Germany and its global allies. Methodology: historiographic, biographical, and historical analysis; reconstruction method; comparative legal method. Conclusions: firstly, historically, the UN Convention on the Prevention of Genocide was the first and most significant international normative legal act at the time of the organization's creation; secondly, despite this, the Universal Declaration of Human Rights, which was adopted a day later, is still considered more significant; thirdly, contrary to obvious facts, the UN Convention on the Prevention of Genocide was not applied to the peoples of the Soviet Union, as those who suffered most from the actions of the Nazis and their accomplices; fourthly, the Universal Declaration of Human Rights has become a document used for political pressure on countries that the United States and Western countries have defined as undemocratic; fifthly, extremism, as a system of radical ideas, views and concepts, inevitably gives rise to genocide, as a phenomenon of mass extermination of people. Scientific and practical significance. The study proves that extremism not only promotes radical views but also inevitably leads to acts of extermination, i.e., genocide.