Why did Kenneth Waltz consider bipolarity a stable international arrangement?

In the context of international relations, Kenneth Waltz’s neorealist theory posits that the structure of the international system—specifically its polarity—is the primary determinant of state behavior.1

Waltz viewed bipolarity as a stable arrangement primarily because it simplified the international system into two opposing blocs, reducing the complexity and unpredictability inherent in multipolar systems. In a bipolar world, the two superpowers are locked in a direct, vigilant rivalry, which minimizes the risk of miscalculation that often arises from shifting, uncertain alliances.123

Furthermore, the stability of this configuration was reinforced by the deterrent effect of nuclear weapons. The prospect of mutual destruction created a powerful incentive for restraint, as both superpowers sought to avoid direct military confrontation that could escalate into a global nuclear conflict. Consequently, while the system remained competitive, the clear distribution of power and the existential risks of war encouraged a level of systemic predictability that Waltz considered more stable than the alternatives.12