In Waltzian perspective, having only two great powers in the system is a sine qua non condition to a stable international environment. “Significant changes take place when the number of great powers reduces to two or one. With more than two, states rely for their security both on their own internal efforts and on alliances they may make with others. Competition in multipolar systems is more complicated than competition in bipolar ones because uncertainties about the comparative capabilities of states multiply as numbers grow, and because estimates of the cohesiveness and strength of coalitions are hard to make”.