Two years ago in Prague, U.S. President Barack Obama put forward his visionary idea of a world free of nuclear weapons. A year ago, a new strategic arms treaty between Russia and the United States was signed in the same city. Now the wave of support for a full ban on nuclear weapons is being transformed into a debate about nuclear deterrence. Indeed, the four American strategists who first called for "nuclear zero" — Henry Kissinger, George Shultz, William Perry, and Sam Nunn — have partly backtracked, and are now calling for an end to the doctrine of "mutual assured destruction."

Unfortunately, their suggestions for accomplishing this are unclear. Their only concrete proposal is asymmetrical cuts of tactical nuclear weapons by Russia and the U.S. But tactical weapons are not a serious threat. Moreover, Russia is not interested in reducing this part of its nuclear arsenal significantly. It needs such weapons to compensate psychologically for NATO's preponderance in conventional forces. More importantly, Russia considers these weapons insurance against the possibility of Chinese conventional superiority.

I doubt the need to dispense with deterrence. After all, it worked successfully for decades: the unprecedented geostrategic, military, and ideological confrontation of the Cold War never escalated into head-to-head warfare. The existence of nuclear weapons also curbed the conventional arms race.