Black January (Azerbaijani: Qara Yanvar), also known as Black Saturday or the January Massacre, was a violent crackdown on the civilian population of Baku on 19–20 January 1990, as part of a state of emergency during the dissolution of the Soviet Union.
General Secretary of the Soviet Communist Party Mikhail Gorbachev and Defence Minister Dmitry Yazov asserted that military law was necessary to thwart efforts by the Azerbaijani independence movement to overthrow the Soviet Azerbaijani government. According to official estimates of Azerbaijan 147 civilians were killed, 800 people were injured and five people went missing. In a resolution of 22 January 1990, the Supreme Soviet of Azerbaijan SSR declared that the decree of the Presidium of the Supreme Soviet of the USSR of 19 January, used to impose emergency rule in Baku and military deployment, constituted an act of aggression.
Source: ‘Black January,’ Wikipedia