The world during the 20th century has witnessed four IR systems.
Dominance of the Great European empires in the 19th century until 1914. In system theory, this period represents a balance-of-power system, but by 1910 it has decayed.
The empires destroy themselves from 1914-1945. With the major countries not willing to respond to threats, this period is termed “anti-balance-of-power” system. These systems are stable and temporary.
The collapse of the traditional European powers leaves the U.S. and the USSR facing each other in a bipolar system (two country system).
The superpowers block and exhaust themselves from 1945 through the 1980s, and the bipolar system falls apart.
The collapse of the Soviet Union end bipolarity, which leaves the world in a disputed era.
Remember….