Passage: The Nagorno-Karabakh War was an ethnic and territorial conflict that took place in the late 1980s to May 1994, in the 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  protracted, undeclared mountain warfare 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 began in a relatively peaceful manner in 1988; in the following months, as the Soviet Union disintegrated, it gradually grew into an increasingly violent conflict between Armenians and Azerbaijanis, resulting in claims of ethnic cleansing by both sides.Inter-ethnic clashes 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 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 early 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 early 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...

Question: When did the Nagorno-Karabakh War end?
May 1994