Abstract. At the beginning of 1988 the Republic of Armenia laid unfounded territorial claims against Azerbaijan in order to occupy Nagorno-Karabakh (Nagorno-Karabakh – it is Russian translation of ”Daghlig Garabagh” that means a mountainous part of Garabagh, that is, ”Upper Garabagh”), which is an indivisible part of the Republic of Azerbaijan. The article analyzes socio-economic, political, and legal aspects of territorial claims of Armenia against Nagorno-Karabakh. At the same time, it provides a source-based examination of the socio-economic development of Nagorno-Karabakh. In addition, based on legal documents, the article proves that until 1991, the Armenians had the highest political, economic and cultural autonomy in this region of Azerbaijan. The article says that having managed to build a mono ethnic state under the USSR, i.e. in 1988-1991, the Republic of Armenia pursued an overt policy of aggression against Azerbaijan, which saw massacres of civilians, destruction, plunder and burning down of settlements. At the same time, the article provides a factual analysis of Armenia’s territorial claims and policy of aggression against Azerbaijan at the end of the 20thcentury.