The establishment of the Soviet regime in the Southern Caucasus between April 1920 and April of 1921 included the solution of ethno-territorial conflicts such as that of Mountainous Gharabagh, which had been in dispute between Armenia and Azerbaijan since 1918.
Soviet Russia had recognized the mountainous area of Gharabagh as a disputed zone and, in August 1920, after an agreement signed by Soviet Russian and the Republic of Armenia, Russian forces had been temporarily deployed in the region.
On November 30, 1920, one day after the Armenian Bolsheviks had proclaimed Armenia as a Soviet republic (the power was actually transferred on December 2), the Revolutionary Committee of Azerbaijan (the highest executive power of the country at the moment) recognized that Gharabagh, Zangezur, and Nakhichevan, territories formerly pretended by Azerbaijan, were indivisible part of Armenia.
The National Council of Azerbaijan, on the basis of the agreement signed by Soviet Azerbaijan and Soviet Armenia, proclaimed Mountainous Gharabagh as indivisible part of Armenia by the declaration of June 12, 1921. On the basis of the November 30, 1920 declaration and the agreement signed by the Soviet governments of Azerbaijan and Armenia, Armenia also made a similar declaration.
The text of the decree approved by the government of Armenia was published in the Armenian and Azerbaijani press (Bakinski rabotchi, organ of the Communist Party of Azerbaijan, June 22, 1921), thus confirming legally the union of Mountainous Gharabagh to Armenia. In the context of international law, this was the last legal act regarding Mountainous Gharabagh during the Communist regime.
The fact was totally overlooked by the Caucasian Bureau of the Communist Party of Russia, which invited to a plenary session on July 4, 1921 in Tbilisi, where the union of Mountainous Gharabagh to Soviet Armenia was confirmed as a fact. However, by suggestion of Moscow and the immediate intervention of Joseph Stalin, the decision of the previous day was revised in the wee hours of July 5 and a new resolution was imposed, which established that Mountainous Gharabagh would be part of Soviet Azerbaijan as an autonomous region. This resolution was an unprecedented legal act in the history of international law, when the party body of a third country (Russia), without any legal grounds or jurisdiction, decided the status of Mountainous Gharabagh after another decision had been agreed before.
The Soviet republics of Azerbaijan and Armenia were included in the process of the formation of the Union of Soviet Socialist Republics in December 1922. Despite the resistance of the Armenian population, on a small fraction of the territory of Gharabagh, by decision of the Central Executive Revolutionary Committee of Soviet Azerbaijan, on July 7, 1923, the Autonomous Region (Oblast) of Mountainous (Nagorno) Gharabagh was formed as part of the Soviet Socialist Republic of Azerbaijan, without having any common borders with Armenia.
This would not solve, but just freeze the question of Gharabagh for the next six decades and half, until the popular explosion of 1988 and the beginning of the Gharabagh movement.