75 Years on, How Will the Nuclear Age End?


Seventy-five years ago, U.S. nuclear weapons devastated Hiroshima and Nagasaki. For individual human beings, 75 years signals nearness to the end of life. But for the nuclear age, does this anniversary mark the beginning, the middle, or the end?

There are two dramatic ways in which the nuclear age could end: annihilation or disarmament. If one ending is undesirable and the other unachievable, leaders should prolong life with nuclear weapons by making their use much less likely and reducing their destructiveness in case they are used. Clearer adherence to the law of armed conflict and greater understanding of the climatic effects of nuclear war would serve both purposes.

Annihilation could come through war involving arsenals that devastated not only the societies of the belligerent countries, but also the agricultural productivity and economic markets on which many other nations depend. Some nations would survive, and some could retain nuclear weapons or ambitions to acquire them, but for the purposes of marking epochs, we could say that the first nuclear age would have ended.



Nuclear disarmament is a much happier prospect. This is one reason that many in Japan and other countries advocate it and support the 2017 Treaty on the Prohibition of Nuclear Weapons. However, the treaty does not detail how nuclear disarmament would be defined, achieved over time, verified, and enforced. Nor have the nine nuclear-armed states done so, even though the Nuclear Non-Proliferation Treaty obligates the United States, Russia, the United Kingdom, France, and China “to pursue negotiations in good faith on effective measures” to end the nuclear arms race and achieve nuclear disarmament. (The Lawrence Livermore National Laboratory’s Center for Global Security Research just published a monograph by Toby Dalton and me that maps quandaries a disarmament regime would need to solve, “Thinking the Other Unthinkable: Disarmament in North Korea and Beyond.”)

The undesirability of nuclear war and the uncertainty about how to accomplish nuclear disarmament suggest that we are still in the middle of the nuclear age. This middle age is predicated on maintaining nuclear deterrence as a livable way to avoid annihilating wars while searching for a disarmament solution. If deterrence could endure without failure, the nuclear age could tolerably last forever.

Yet, nuclear deterrence could fail. Indeed, the risk of failure — nuclear war — is what makes deterrence work. Everyone would be more secure if deterrence could be maintained with significantly less destructive arsenals. Nations that do not possess these weapons (or participate in alliances that do) are especially keen to be spared from the consequences of other governments’ nuclear wars.

Russian President Vladimir Putin’s response to an interviewer’s question two years ago epitomized the vulnerability felt by non-nuclear-weapon states. Putin said that if Russia’s warning systems detected an enemy attack with nuclear-armed missiles, he would order “reciprocal” nuclear strikes. “If there is this decision to destroy Russia then we have a legal right to respond,” Putin said. “Yes,” he acknowledged, “this would be a global catastrophe for humanity but I, as a citizen of Russia and the head of the Russian state, would like to ask you this — what do we need a world for if there is no Russia in it?”

In their renewed arms race, Russia and the United States — and increasingly China, India, and Pakistan — let the theoretical logic of deterrence and the interests of military-industrial establishments rationalize how many nuclear weapons of what type and which targets they “need.” This thinking is too narrow. It does not ask, in the words of Paul Ramsey’s classic, The Just War, what is “the upper limit of sanity in the actual use of nuclear weapons”?

Two considerations beyond deterrence might help answer this question: What number and type of nuclear weapons, detonated on which targets, would be likely to produce environmental and climatic effects that would threaten the viability not only of the “winning” combatant country but also of non-belligerent nations? And what scale of nuclear war would clearly transgress the law of armed conflict (also known as international humanitarian law)?

Data and models to assess the potential climatic effects of nuclear war have improved enormously since the prospect of “nuclear winter” first emerged in the 1980s. It is time for the United States, Russia, China, India, and Pakistan (at least) to conduct new studies examining the probable climatic effects of various scenarios that drive their planning for potential nuclear war. Declassified versions of such studies should be made available for international experts to analyze and debate.

If reputable scientific debate indicates little risk of agricultural catastrophe, then nuclear-armed states would have a stronger basis for retaining the weapons and policies that could produce those scenarios. (Other arguments for disarmament still could be validly made.) Conversely, if openly debated scientific studies identify scenarios that would be catastrophic not only to the belligerent nations but also to others, then it should be more difficult to justify retaining arsenals and war plans that are likely to produce such harm.

Similarly, it is time to clarify whether and how the use of nuclear weapons can comport with the law of armed conflict. For decades, officials in the United States have declared that these weapons are not aimed “at population per se,” or that operations would spare cities “to the degree practicable.” The fuzzy language about targeting represents an important and admirable fealty to the law of armed conflict. Nevertheless, U.S. and other states’ war plans have called for detonating hundreds of weapons on targets in cities, which would stretch any definition of legality.

The Trump administration’s 2018 Nuclear Posture Review (like the Obama administration’s before it) affirms America’s commitment “to adhere to the law of armed conflict [in any] initiation and conduct of nuclear operations.” However, it does not explain how this would be done. The United Kingdom’s position is similar, while the other seven nuclear-armed states are even less forthcoming.

Because nuclear-armed states insist that they are responsible stewards and retain these weapons only for legitimate defensive purposes, they should be willing to explain whether and how they plan to adhere to the law of armed conflict in the potential conduct of nuclear operations. They should describe how variations in explosive yields and numbers of weapons and their targets could increase or decrease the probability that use of nuclear weapons would comport with the law of armed conflict.

Arsenals and policies that comport with the law of armed conflict would provide more credible and therefore more effective deterrence. A state that has worked through and publicly articulated why and how its policies would be legal would presumably be less self-deterred. This added credibility could inform adversaries’ deliberations in deciding whether to undertake escalatory actions up to and during nuclear exchanges.

The government of Japan and the governments that defend or potentially threaten it are not prepared to live without nuclear deterrence. By adding environmental and legal considerations to the logic of deterrence, they could greatly reduce the horrific consequences of its failure. Nuclear war with current arsenals would make the suffering of Hiroshima and Nagasaki seem minor by comparison.



George Perkovich is the Olivier and Nomellini chair and vice president for studies at the Carnegie Endowment for International Peace, and author most recently of Toward Accountable Nuclear Deterrents: How Much is Too Much?           

Image: U.S. Department of Energy