The Nagorno-Karabakh War was an armed conflict that took place from February 1988 to May 1994 , in the small ethnic enclave of Nagorno-Karabakh in southwestern Azerbaijan , between the mostly ethnic Armenians of Nagorno-Karabakh backed by the Republic of Armenia against the Republic of Azerbaijan . 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 .