NFU modeling fails and causes conflict.

Detractors, on the other hand, do view NFU as a dangerous folly.

Among the general criticisms of such an approach are that it would leave the U.S. without the ability to deter non-nuclear non-conventional attacks (involving, say, biological or chemical weapons); that such restraint would not be credible in the eyes of potential adversaries who would always have to assume that the U.S. would retain a practical first-use option; and that there is no reason to believe that other nuclear powers would follow suit.

But in today’s world of great power competition and near-peer rivals, perhaps the most telling criticism of NFU is that such a posture would weaken deterrence against conventional attack. Here the logic is both straightforward and compelling. Although the United States remains the world’s most powerful conventional military power, in recent years China and Russia have made dramatic gains in conventional capabilities. 

Indeed, they may well have achieved local military superiority over the United States and its allies in some parts of the world. As a result, Washington cannot casually assume that U.S. and allied conventional forces would be sufficient to deter China or Russia from exploiting their local advantages and launching a conventional attack against America’s regional allies and interests.

Absent the threat of American first use of nuclear weapons, the advantage would thus lie with the aggressor, who would not have to factor even the possibility of the U.S. using nuclear weapons to reverse its early conventional military successes. But the possibility that those early successes might trigger the use of U.S. nuclear weapons on the battlefield – and that this might escalate to a general strategic nuclear exchange – would change the equation significantly.