Ethnic tensions had escalated between the Armenians and Azerbaijanis in spring and summer 1988. On January 9, 1990, after the Armenian parliament voted to include Nagorno-Karabakh within its budget, renewed fighting broke out, hostages were taken, and four Soviet soldiers were killed. On January 11, Popular Front radicals stormed party buildings and effectively overthrew the communist powers in the southern town of Lenkoran. Gorbachev resolved to regain control of Azerbaijan; the events that ensued are known as "Black January." Late on January 19, 1990, after blowing up the central television station and cutting the phone and radio lines, 26,000 Soviet troops entered the Azerbaijani capital Baku, smashing barricades, attacking protesters, and firing into crowds. On that night and during subsequent confrontations (which lasted until February), more than 130 people died – the majority of whom were civilians. More than 700 civilians were wounded, hundreds were detained, but only a few were actually tried for alleged criminal offenses.

Which two groups saw increasing ethnic conflicts in 1988?