Liviu Horovitz
Dr, Associate
International Security Research Division, German Institute for International and Security Affairs (SWP)
Germany
That the United States should use nuclear weapons for the sole purpose of deterring and, if necessary, responding to nuclear attacks is, on first sight, a reasonable and appealing idea. Who would want to use nuclear weapons first? Who would not want to diminish the role of these terrible means of destruction? No wonder US President Joe Biden came into office keen to declare a “sole purpose” policy. And yet, simple solutions are often deceptive. Altering the nuclear doctrine would have had questionable benefits but certain costs. Ultimately, a change proved incompatible with the Administration’s desire to strengthen US alliances at a time of increasing insecurity. Nonetheless, future US policymakers will continue to struggle with this deeply uncomfortable policy choice.
The current US policy of nuclear ambiguity helps reinforce deterrence and reassurance, but puts US leaders in a difficult position. Numerous countries rely on Washington for security, but deployed US forces are rarely sufficient to rebuff an invasion. Hence, allies have to believe Washington’s promise to reinforce quickly in case of an attack. Keeping the option open to potentially respond with nuclear weapons complicates adversaries’ calculations, even if the probability of Washington doing so is very low. Also, such ambiguity strengthens reassurance: The United States accepts some risk that a conventional conflict might escalate to general nuclear war, thereby suggesting that allies are worth defending. US credibility to actually use atomic arms may be low, but reassurance is incremental – no matter how imperfect, more is simply better than less.
The status quo does come with costs and, potentially, with risks. The political dimension is most important: Keeping the option open to use nuclear weapons tells domestic audiences that war abroad would not just involve human casualties and financial costs, but potentially also risk horrendous nuclear destruction at home. In addition, critics claim that in a crisis, adversaries would fear a US disarming nuclear first strike. Arguably, this could force opponents to use their weapons before losing them. Also, Washington’s ambiguity might facilitate misperceptions and accidentally trigger nuclear war. Last but not least, “sole purpose” advocates often argue that a change of US declaratory policy would further the goal of nuclear disarmament.
The reality is that most benefits of a sole purpose declaration could only be achieved if the United States fundamentally altered its nuclear forces. Strategic deterrence concerns, however, rendered such arsenal changes quasi impossible for the Biden Administration. Purely declaratory changes could have yielded some political benefits as domestic audiences indeed might have been assuaged by such public statements. Yet merely saying that one would not use nuclear weapons first would not have persuaded adversaries; and if Russia or China considered the US declaration untrustworthy, such a statement would have neither reduced the risk of nuclear escalation nor diminished the probability of nuclear accidents. It also remains unclear why a declaratory policy change would have delivered decisive bargaining advantages within various nuclear disarmament fore.
In contrast to questionable benefits, allies’ concerns weighted heavily. Biden officials consulted broadly and frequently in both Europe and Asia, where they were confronted with similar concerns. Although allies argued that “sole purpose” would not affect Washington’s ability to deter Chinese or Russian conventional aggression as neither Beijing nor Moscow were likely to believe a purely declaratory policy change, they highlighted the political consequences of such a policy. Especially in Asia, where some questioned the US ability to prevail conventionally against China, many worried that a US sole purpose doctrine would signal that Washington would rather accept conventional defeat than engage in nuclear escalation. In Europe, in turn, the question was one of resolve more than of capabilities – allies were concerned that “sole purpose” could be seen to imply that Washington would hesitate to reinforce conventionally in case of an attack.
Ultimately, the White House revived and revised Barack Obama’s posture. Even before Russia invaded Ukraine, the Administration concluded that it was not the right time for a change. When finally published, the review declared that the “fundamental” purpose of US nuclear weapons was to deter nuclear attacks on the United States and its allies. Washington would only consider nuclear use in “extreme circumstances.” For now, the questions has been settled – but not for long. The Administration noted that it retained the goal of moving towards a sole purpose declaration in the future. It pledged to work with allies to identify the concrete steps that could enable Washington to proceed with such a policy change. Whether a future Administration will manage to implement such steps, remains to be seen.