In May 1918, following the withdrawal of the Russian army from the South Caucasus, Armenia, Georgia and Azerbaijan, until then part of the Tsarist Empire, declared their independence.
The Paris Peace Conference recognized de facto Armenia and asked the American President Widrow Wilson to define the borders by an arbitration award. The same conference refused Azerbaijan's request for recognition because of its unrealistic claims to Georgian and Armenian territories: Armenia and Azerbaijan were opposed to each other over the question of the ownership of Karabakh and Nakhchivan, which thus remained unresolved.
In 1920, the two countries were occupied by the Red Army and Sovietized.
In 1921, after a decision in favor of the attachment of Karabagh to Armenia, the Bolshevik party radically changed its position under the personal pressure of Stalin. In view of the ethnic and linguistic proximity between the Turks and the inhabitants of Azerbaijan, and anxious to use Mustapha Kemal for the expansion of communism in the Turkish-speaking world, Stalin ordered the attachment of two regions to Azerbaijan: Nakhchivan, with a relative majority of Armenians, and Karabakh, inhabited almost exclusively by Armenians.
This decision by a political party of a third state, the Communist Party of Russia, without any legal basis or legitimacy, is an unprecedented act in the history of international law.
In 1923, following the USSR's decree to create the Oblast/Autonomous Region of Nagorno-Karabakh (RAHK), Azerbaijan annexed the lower part of Karabakh, thus appropriating large districts of its lowland territory, while artificially removing the territorial continuity of the autonomous region with Armenia.
The Nagorno-Karabakh Autonomous Region thus became an enclave within Azerbaijan, cut off from Soviet Armenia.
Throughout the Soviet period, faced with discrimination of all kinds, and in particular faced with the deliberate economic and demographic policy of "disarming" the region by the Azerbaijani administration, the Armenian population of Nagorno-Karabakh did not cease to ask for its attachment to Armenia, undergoing in return successive waves of purges, deportations and executions.
In the days of Gorbachev's Glasnost and Perestroika, the deliberately discriminatory policy of the Soviet Azerbaijani authorities had already succeeded in emptying Nakhchivan and the regions annexed by Azerbaijan in the Karabakh plain of its Armenian population, but it had not had the same success in the RAHK (Autonomous Region of Nagorno-Karabakh), where 85% of the Armenians were still living.
Thus, on February 20, 1988, three years after the advent of Perestroika, the Soviet of the RAHK voted for the attachment of Nagorno-Karabakh to Armenia, in full compliance with Soviet legislation. But this democratic and legal choice is rejected by the Central Committee of the Communist Party of the USSR. Soviet Azerbaijan, for its part, responded to this peaceful demand with a series of pogroms of Armenians all over the territory of Azerbaijan: Sumgait, Baku, Kirovabad, Chamakhi, Chamkhor, Mingechaur. A new phase of ethnic cleansing of Armenians was then initiated with the deportation of Armenian populations everywhere, including in the RAHK, which resulted in the forced departure of 450,000 Armenians from Azerbaijan, and 180,000 Azerbaijanis from Armenia.
Between 1991 and 1993, from the military bases in Shushi and Khojalu airport, Azerbaijan bombed the civilian population of Armenian localities on a daily basis, especially in the capital Stepanakert, where the inhabitants lived in underground tunnels for almost 3 years.
From April-August 1991, the operations of the Soviet internal armed forces (OMON), together with the Azerbaijani forces, organized the deportation of Armenians from Nagorno-Karabakh, bombing Armenian towns and villages. These operations soon turned into a full-scale attack on Armenians. In June 1992, Azerbaijani forces occupied 40% of the territory of Nagorno-Karabakh and displaced 66,000 of the region's population. In the village of Maragha alone, more than 100 civilians were massacred by the Azeri armed forces. The Armenian resistance was organized. On two occasions, in 1992 and 1994, large-scale attacks by Azerbaijani forces failed.
On 31st August 1991, Armenia and Azerbaijan declared their independence from the collapsing USSR. Azerbaijan declares itself as a successor state to the independent Republic of Azerbaijan of 1918-1920 which did not include Karabakh, taking care to remove at the same time the status of autonomy of Nagorno-Karabakh which it declares an integral part of its territory.
Two days later, on 2 September 1991, noting the dissolution of the USSR, the local authorities of Nagorno-Karabakh proclaimed independence in their turn, creating a distinct self-determined republic in the region. A referendum ratified this independence on 10 December 1991 (International Human Rights Day).
In May 1993, the Armenian self-defence forces succeeded not only in repelling the aggressions, but also in creating a security zone around Nagorno-Karabakh, while opening up the region by opening the road to Armenia.
The conflict ended with a victory for the Armenian side and a ceasefire was signed with Russian mediation in Bishkek, Kyrgyzstan, on 12 May 1994 by representatives of Armenia, Azerbaijan and the Nagorno-Karabakh Republic.
Two years earlier, the CSCE (later OSCE) had established the Minsk Group with a threefold French, American and Russian co-chairmanship, with the aim of achieving a peaceful and negotiated solution to the Nagorno-Karabakh conflict.
During its 26 years of work to avoid a new war in Nagorno-Karabakh, the Minsk Group has evolved its principles to find a solution based on both the principles of the right to self-determination of Nagorno-Karabakh and the territorial integrity of Azerbaijan.
On 27 September 2020, taking advantage of the period of crisis due to the global coronavirus pandemic (COVID-19), and the paralysis of American political life due to the US elections, the army of Azerbaijan, with the direct participation of Turkey and the deployment of Syrian mercenaries provided by the latter, launched a large-scale armed aggression against Nagorno-Karabakh along the entire length of the contact line.
The war lasted for 44 days, killing nearly 5,000 people on the Armenian side. Azerbaijan has never published the numbers of its soldiers killed.
The conflict ended in an Armenian defeat and more than 200 prisoners of war were captured by Azerbaijan.
Since the end of the war, on 12 May, 5 November 2021 and 13 September 2022, the Azerbaijani army has made several incursions occupying at least 215 square kilometers of sovereign territory of Armenia itself, resulting in hundreds of casualties and prisoners, including several dozen victims of summary executions have been documented by international human rights organizations.