Context from Wikipedia (because the article doesn't have it):

"The main combatants were Azerbaijan, with support from Turkey and foreign mercenary groups on one side; and the self-proclaimed Republic of Artsakh and Armenia, on the other. It was the latest escalation of an unresolved conflict over the region, which was annexed to Azerbaijan during the Soviet era and internationally recognized as part of Azerbaijan, but partially governed by Artsakh, a breakaway state with an Armenian ethnic majority."