The Nagorno-Karabakh War was an armed conflict that took place from February 1988 to May 1994, in the small enclave of Nagorno-Karabakh in southwestern Azerbaijan, between the majority ethnic Armenians of Nagorno-Karabakh backed by the Republic of Armenia, and the Republic of Azerbaijan. As the war progressed, Armenia and Azerbaijan, both former Soviet Republics, entangled themselves in a protracted, undeclared war in the mountainous heights of Karabakh as Azerbaijan attempted to curb the secessionist movement in Nagorno-Karabakh. The enclave's parliament had voted in favor of uniting itself with Armenia and a referendum, boycotted by the Azerbaijani population of Nagorno-Karabakh, was held, whereby most of the voters voted in favor of independence. The demand to unify with Armenia, which proliferated in the late 1980s, began in a relatively peaceful manner; however, in the following months, as the Soviet Union's disintegration neared, it gradually grew into an increasingly violent conflict between ethnic Armenians and ethnic Azerbaijanis, resulting in claims of ethnic cleansing by both sides.
Inter-ethnic fighting between the two broke out shortly after the parliament of the Nagorno-Karabakh Autonomous Oblast (NKAO) in Azerbaijan voted to unify the region with Armenia on 20 February 1988. The circumstances of the dissolution of the Soviet Union facilitated an Armenian separatist movement in Azerbaijan. The declaration of secession from Azerbaijan was the final result of a territorial conflict regarding the land. As Azerbaijan declared its independence from the Soviet Union and removed the powers held by the enclave's government, the Armenian majority voted to secede from Azerbaijan and in the process proclaimed the unrecognized Republic of Nagorno-Karabakh.
Full-scale fighting erupted in the late winter of 1992. International mediation by several groups including the Organization for Security and Co-operation in Europe (OSCE) failed to bring an end resolution that both sides could work with. In the spring of 1993, Armenian forces captured regions outside the enclave itself, threatening the involvement of other countries in the region. By the end of the war in 1994, the Armenians were in full control of most of the enclave and also held and currently control approximately 9% of Azerbaijan's territory outside the enclave. As many as 230,000 Armenians from Azerbaijan and 800,000 Azeris from Armenia and Karabakh have been displaced as a result of the conflict. A Russian-brokered ceasefire was signed in May 1994 and peace talks, mediated by the OSCE Minsk Group, have been held ever since by Armenia and Azerbaijan.