Original:  At the end of the 20th century there were extreme nationalistic interpretations of Balkan and Caucasus history, which became powerful weapons in ethno-territorial conflicts and accelerated disintegration of multinational states like Yugoslavia and the Soviet Union.
Revised:  At the end of the 20th century were extreme nationalistic interpretations of Balkan and Caucasus history, which became powerful weapons in ethno-territorial conflicts and accelerated disintegration of multinational states like Yugoslavia and the Soviet Union.
Edit intent: clarity