The region became part of the Russian Empire at the start of the 19th century. However, following the Russian Revolution in October 1917, it was awarded to the Azerbaijan Soviet Socialist Republic as an autonomous region – a decision opposed by the neighboring Armenian Soviet Socialist Republic and by the Armenian inhabitants of Nagorno-Karabakh.
In September 1991, as the Soviet Union collapsed, Nagorno-Karabakh provisionally declared independence. In response, the Azerbaijani Government rescinded its autonomy and launched a military assault to end the rebellion.
In January 1992, following a referendum, it formally declared independence as the Nagorno-Karabakh Republic. Stepping up its military offensive, Azerbaijan recaptured much of the region.
However, the following year, Armenian and Nagorno-Karabakh forces not only retook the land that was lost, but they also captured a large swathe of territory around Nagorno-Karabakh, which still remains occupied by Armenia to this day.
Despite this, Armenia and Azerbaijan have agreed on a set of principles to resolve the conflict. These include returning territory to Azerbaijani control, opening a land corridor between Nagorno-Karabakh and Armenia, and determining the final legal status of Nagorno-Karabakh through a legally binding expression of will.
To date, however, the conflict remains unresolved. More to the point Nagorno-Karabakh remains wholly unrecognized on the world stage. Indeed, it isn’t even formally recognized by Armenia; not least of all because Azerbaijan’s territorial integrity has repeatedly been reaffirmed by the UN Security Council.
In the meantime, there’s a genuine worry internationally that the dispute may well lead to war, not least of all because Armenia and Azerbaijan have been caught up in an arms race and have also occasionally engaged in serious fighting, most recently in October 2020.