Balance of threat

The balance of threat (BoT) theory was proposed by Stephen M. Walt first in an article titled "Alliance Formation and the Balance of World Power" published in the journal International Security in 1985 and later further elaborated in his book "The Origins of Alliances" (1987). The balance of threat theory modified the popular balance of power theory in the neorealist school of international relations.

According to balance of threat theory, states' alliance behavior is determined by the threat they perceive from other states. Walt contends that states will generally balance by allying against a perceived threat, although very weak states are more likely to bandwagon with the rising threat in order to protect their own security. He points to the example of the alliance patterns of European states before and during World War I and World War II, when nations with a significantly greater combined power allied against the recognized threat of German expansionism.

Walt identifies four criteria states use to evaluate the threat posed by another state: its aggregate strength (size, population, and economic capabilities), its geographic proximity, its offensive capabilities, and its offensive intentions. Walt argues that the more other states view a rising state as possessing these qualities, the more likely they are to view it as a threat and balance against it.

Balance of threat theory modified realism (as well as the neorealism of Kenneth Waltz) by separating power from threat. In balance of power theory, which had previously dominated realist analyses, states balance against others whose power (i.e., military capabilities) was rising—greater power was assumed to reflect offensive intentions. Walt argues that this is not borne out by empirical evidence, and that balance of threat theory—in which states will not balance against those who are rising in power but do not display offensive intentions—gives a better account of the evidence. For instance, the United States was most powerful of the two superpowers during the Cold War, but, contrary to the balance of power theory, more states (e.g., the NATO nations) allied with it than with the Soviet Union because the United States displayed much less aggressive intentions toward them than did the Soviet Union.

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