Nagorno-Karabakh is a region in Azerbaijan with a 75% Armenian majority in 1990. Following the Nagorno-Karabakh War, Nagorno-Karabakh is under the control of the winner, Armenia, and all the minroityies have fled, leaving a population of 140,000 Armenians.
The most serious problem between the short-lived Transcaucasian republics of Armenia and Azerbaijan was over the republics' claims to a mountainous region called Karabagh (and after 1920 the Nagorno-Karabakh Autonomous Oblast of the USSR). Britain, which occupied Transcaucasia after World War I, decided in favor of Azerbaijan in the summer of 1919. The settlement remained in force after the Red army took over both republics in 1920, but the Soviets were never able to resolve the dispute, which exploded into war as soon as both nations became independent. 
- Chorbajian, Levon, et al. The Caucasian Knot: The History and Geopolitics of Nagorno-Karabagh. (1994). 198 pp.
- Artin H. Arslanian, "Britain and the Question of Mountainous Karabagh," Middle Eastern Studies 1980 16(1): 92-104.