Correspondence: Responding to Chemical and Biological Threats

The Author Replies:

The official U.S. government policy is to maintain “calculated ambiguity” about whether the United States would retaliate with nuclear weapons in response to an adversary’s use of chemical weapons (CW) or biological weapons (BW) against U.S. allies, U.S. armed forces overseas, or the U.S. homeland. Since the 1991 Gulf War, numerous civilian and military leaders have stated that the United States might use nuclear weapons in response to CW and BW threats or attacks, and some have even stated that the United States will use nuclear weapons in such circumstances. ¹ The central argument in my spring 2000 International Security article was that this policy has created a dangerous “commitment trap” problem. ² The benefit of making such nuclear threats, whether stated ambiguously or clearly, is that they can increase an adversary’s estimate of the probability that the U.S. president would order nuclear retaliation, which should therefore decrease the likelihood of chemical or biological weapons attacks. But there is a serious cost attached to this obvious benefit: If deterrence fails despite nuclear threats, the statements will also increase the likelihood that the United States will actually use nuclear weapons, because the president’s personal and the U.S. government’s institutional reputations for following through on threats would be perceived to be at stake. I argued that current U.S. nuclear doctrine has therefore created a subtle dilemma that has not been recognized, much less debated, in both policy and academic circles: Is the improvement in the U.S. ability to deter CW and BW threats worth the increased likelihood of a U.S. nuclear response if deterrence fails?

I welcome Susan Martin’s entry into this important debate about U.S. nuclear weapons doctrine. ³ Martin makes two central arguments in her critique of my article. First, she disputes my claims that a serious commitment trap problem exists. She argues that a state’s and statesman’s reputations depend on whether they respond effectively to chemical or biological attacks, not on whether they use the particular means (i.e., nuclear weapons) that they earlier threatened to use. Hence she concludes that my recommendation to rely on threats of devastating conventional retaliation in response to CW or BW use contradicts my theoretical analysis. Either the proposed conventional retaliation will be ineffective, in which case the United States should not have followed my recommendation; or it will be effective, in which case there was no problem of commitment trap to begin with because the president’s and government’s reputation would not have suffered.

Martin’s argument is clever, but not compelling. For what influences the likelihood of a U.S. president ordering the use of nuclear weapons is not the final outcome of a retaliatory strike as determined by scholars after the conflict, but rather the president’s perceptions at the time of decision during the crisis about the likely outcomes of various military options under consideration. As long as a nuclear decisionmaker believes that backing away from threats will damage his or her personal reputation or the nation’s credibility in crises, it will influence his or her behavior regardless of what scholars later determine to be the final impact of decisions on reputation. ⁴

Nuclear threats are a double-edged sword. The deterrent benefit and the danger, if deterrence fails, result from the same factor: Threats create an extra element of commitment, increasing the incentive for the president to use nuclear weapons. The costs produced by the commitment trap are, ironically, most clear in ambiguous situations. If a president was absolutely certain that retaliatory strikes with conventional weapons would be effective against an adversary, there would be little need for a nuclear response. If the president was absolutely certain that only nuclear retaliation would be effective, then the incentive to use nuclear weapons would be considerable regardless of what he or she or other officials had previously said. The impact of the extra incentive to use nuclear weapons, due to the commitment trap, will therefore be greatest when the president is least sure about whether...