1921: An autonomous
Having occupied Armenia and Azerbaijan, the Bolsheviks declare Nagorno-Karabakh an autonomous region within Soviet Azerbaijan. The Armenians, who constitute 94 percent of the enclave’s population, contest the decision. The Soviet Union keeps a lid on Armenian-Azeri tensions.

Mikhail Gorbachev’s reforms embolden the Karabakh Armenians. Demonstrators demand the unification of Nagorno-Karabakh with Soviet Armenia. The protests rattle Baku and leave the Kremlin floundering.

1987: Mass demonstrations
1988: Pogroms
Armenian authorities in Nagorno-Karabakh formally request the region’s transfer to Soviet Armenia. Anti-Armenian violence in the Soviet Azeri city of Sumgait claims at least 30 lives and triggers an exodus of Armenians from Azerbaijan. A few months later, Armenians are attacked in Kirovabad, Azerbaijan.

1990: Black January
As fresh anti-Armenian violence flares in Baku, Mikhail Gorbachev sends in 26,000 troops to quell the Azerbaijani pro-independence movement. Around 100 Azeris are killed in the crackdown.
1991: Karabakh declares independence
The USSR collapses. Armenia and Azerbaijan become independent. Azerbaijan abolishes Nagorno-Karabakh’s autonomous status, fearing that Karabakh Armenian claims will endanger the Azeri minority. In September, Armenian authorities declare Karabakh’s independence.

1991-1994: War
Armenian-Azeri tensions escalate into all-out war. In 1992, the massacre of Azeri civilians in Khojali causes outrage. The conflict kills around 30,000 people and creates about 350,000 Armenian refugees (according to Soviet figures), as well as approximately 600,000 Azeri internally displaced people (according to the UNHCR).

1994: Ceasefire
The two sides sign a truce. Armenian forces have gained the upper hand, holding around 13 percent of Azeri territory. That includes the former Soviet Autonomous Region of Nagorno-Karabakh and a buffer zone around it that links Karabakh to Armenia. The UN calls on Armenian forces to withdraw. The OSCE (Organization for Security and Co-operation in Europe) begins years of mediation efforts.

1998: Ter-Petrossian resigns
The president of Armenia, Levon Ter-Petrossian, resigns after his inner circle rejects a proposed peace deal on Karabakh. He is succeeded by a string of leaders who take a harder line on concessions to Azerbaijan.

2001: Peace within reach
Azeri President Heydar Aliyev and Armenian President Robert Kotcharian come close to a deal in talks at Key West, Florida, but fail to sell it to their respective populations.

2004: Axe murder
Azeri officer Ramil Safarov beheads Armenian classmate Gurgen Markarian with an axe during a NATO training seminar in Hungary. Markarian is sleeping at the time. Safarov is tried and jailed in Hungary.
2011: Failed Russian mediation
Russian president Dmitri Medvedev fails to secure agreement for a peace plan in Kazan, Russia.
2012: The axe killer returns
Ramil Safarov is transferred to Azerbaijan to serve out the rest of his sentence. But he is pardoned and made a national hero by the Azeri president. The decision causes outrage in Armenia.