Words are dangerous, too

Russian President Vladimir Putin will probably not drop an atomic bomb on Ukraine, if only because doing so would prove exceptionally costly for Russia and the world. But his words have consequences, and in threatening to use nuclear weapons, reaching for shock effect, Mr. Putin is venturing into extreme recklessness.

Russia possesses up to 2,000 nonstrategic or tactical nuclear weapons, mostly designed for relatively short-range use on a battlefield or for defensive systems. Bombs to be dropped from planes and warheads for missiles are held in reserve, in central storage depots, on which the United States presumably keeps close watch. These tactical nuclear weapons have never been limited by treaty.

Without any doubt, the use of a nuclear weapon in Ukraine would create a humanitarian cataclysm. As Paul Craig and John Jungerman noted in a history of the arms race, “The overwhelming fact of the nuclear fire is that it is more powerful by a factor of 10 million to 100 million than chemical fires,” such as those in conventional weapons. The blast, heat and radiation from a nuclear bomb could easily spread beyond Ukraine to endanger lives in Russia and elsewhere. This grim prospect of blowback might restrain Mr. Putin, if he is thinking rationally. Also, Mr. Putin cannot simply launch nuclear weapons with the push of a button; there are other people, including the defense leadership, involved in the process.

At the same time, Russia’s military and security forces have so far apparently not slowed Mr. Putin’s disastrous war adventure.

Even if Russia is not likely to use a nuclear weapon, Mr. Putin’s threats are disquieting and irresponsible. An atomic bomb has not been used in combat since 1945. One reason: deterrence, the “cocked pistols” confrontation of the superpowers. These mountains of nuclear warheads were eventually reduced as the Cold War ended, but historian Nina Tannenwald has shown that beyond deterrence, the utter destructive nature of nuclear weapons reinforced a powerful taboo—a revulsion—against actual military use. The frightening experience of the Cuban missile crisis and periodic false alarms throughout the nuclear age no doubt deepened the taboo. Russia’s latest nuclear deterrence principles, approved by Mr. Putin in 2020, say cautiously that a nuclear weapon can be used only if the country is under nuclear attack or “the very existence of the state is in jeopardy.” Mr. Putin now jumps beyond this.

Bluff or not, he escalates danger for all. The Biden administration is right to deliver private warnings to Mr. Putin of grave consequences for nuclear use. Mr. Putin should remember the wise words of Ronald Reagan and Mikhail Gorbachev in 1985 that “a nuclear war cannot be won and must never be fought.”