When and under what circumstances did the USSR collapse?

The USSR collapsed in 1991. The republics began to break away from the once great country. The Baltic countries were the first to break away in 1989, and then all the others. And the reason for this was the crisis that came in the country as a result of the incorrect and illiterate reforms carried out by Gorbachev, which led to big economic problems, a deficit, a halt in industry and a crisis of power. It was also facilitated by the fact that oil prices on the world market fell sharply during this period.