Do Small Arsenals Deter?

To the Editors (Rajesh M. Basrur writes):

Ward Wilson's article "The Winning Weapon? Rethinking Nuclear Weapons in Light of Hiroshima" provides a startling explanation for the end of World War II in East Asia.¹ Wilson argues that, contrary to established wisdom, Japan's decision to surrender stemmed not from the atomic bombing of Hiroshima and Nagasaki but from the Soviet Union's declaration of war against Japan on August 8, 1945. He bases his argument on the following propositions: (1) in the context of the massive destruction caused by the conventional bombing of Japanese cities at the time, the atomic bomb was not qualitatively different; (2) the havoc caused by these attacks did not undermine Japan's determination to press on with the war in hopes of obtaining favorable terms of surrender; (3) the Japanese leadership's reaction to the devastation of Hiroshima does not reflect a perception that the atomic bomb was decisive in its effects; and (4) in contrast, the entry of the Soviet Union into the war, by eliminating available options for a favorable end, compelled Japan to surrender quickly. Wilson's analysis concludes that small nuclear arsenals may not deter aggressors. Whereas large nuclear forces may have such a capability (200 weapons is where the author draws the line), "the logic of deterrence may be different where small arsenals are concerned. If destroying one or two cities does not coerce an opponent, then perhaps the threat of limited nuclear retaliation does not deter when the stakes are high enough" (p. 179). In short, small nuclear powers are inherently unstable and, logically (though the author does not state this explicitly), such states can achieve deterrence stability only if they expand their armories.

Wilson's basic argument about the Japanese decision is a plausible one, drawing considerable evidence from archival sources, though it is thin with respect to the Soviet factor, as only a single source is cited (pp. 174–175). I question, however, his inference regarding the requirements of deterrence today. Contrary to Wilson's claim, the size of a nuclear arsenal does not matter, and more specifically, small arsenals are adequate for obtaining deterrence. A review of how nuclear powers behave when war is nigh demonstrates that the concept of "assured second-strike capability" based on the capacity to inflict casualties into the millions is a mythical notion that does not accord with historical fact. Wilson claims that the "field of nuclear weapons scholarship is like a large structure standing precariously on only a handful of support posts" (p. 177). On the contrary, there is a well-developed literature on how states with nuclear weapons actually behave when the probability of war is significant.² In practice, states approaching nuclear conflict invariably retreat from confrontation regardless of the precise equation they face. In the case I recount below—the crisis-prone relationship between India and Pakistan—it is clear that minimal arsenals are sufficient to deter.

Wilson's extrapolation from the Hiroshima case ignores a crucial element: timing. The author correctly notes that the difference between the effects of massive Allied conventional bombing of Japanese cities and those of the Hiroshima bombing was not more than a factor of three to four (p. 168).³ What he does not appreciate—and I stress this particularly in the context of small nuclear arsenals—is that the Hiroshima bomb was dropped at the end of several years of an extraordinarily costly conventional war that took tens of millions of lives. Any decisionmaker contemplating a nuclear conflict today must begin with an estimate of millions of potential losses within hours or days of the commencement of war. It takes a lot to believe that—barring deterrence for survival—a decisionmaker would conceive of political advantage accruing from the first use of nuclear weapons. But let me not rely on inference alone. What is the evidence with regard to the deterrent effectiveness of small nuclear arsenals?

As a rule, one cannot entirely rely on participants' accounts of a historical event because they have a stake in the historian's...