As Russian President Vladimir Putin marched his army into Ukraine on February 24, he issued dire warnings to the West. Any state that sent its troops to fight Russia, he said, would face “ominous consequences”—the likes of which the world has “never seen in [its] entire history.” His country was ready to act and had made “the necessary decisions” to respond if attacked. “I hope that my words will be heard,” he declared.

Putin didn’t explicitly state what those consequences would be, or what attacks he had in mind. But to anyone listening, the message was clear enough. If the West directly intervened in Ukraine, Russia would use its nuclear arsenal.

Putin’s invocation of nuclear war has reignited debates about deterrence and the utility of nuclear weapons. It has led Admiral Charles Richard, the commander of the U.S. Strategic Command responsible for nuclear deterrence, to argue that the United States may need more nuclear weapons to deter and defend against Russia and also China, which are both modernizing their nuclear forces. “We do not necessarily have to match weapon for weapon,” he said in March. “But it is clear what we have today is the absolute minimum.” Proponents of a nuclear buildup point out that in the coming years, China could rapidly acquire more nuclear weapons, or that Iran, a newcomer, could develop and deploy them for the first time. The United States, the argument runs, risks weakening its own security if it doesn’t amass a larger nuclear arsenal to maintain its advantage over rivals.

But it would be a mistake for the United States, or any state, to embark on a nuclear arms race during this time, when a revolution is afoot in other types of military technology. New defense innovations promise not just to transform warfare but also to undermine the logic and utility of nuclear weapons. With advances in sensing technology, states may soon be able to track and target their adversaries’ nuclear missiles, making the weapons easier to eliminate. And with nuclear weapons more vulnerable, innovations such as drone swarms—large numbers of small automated weapons that collectively execute a coordinated attack—will increasingly define war. A fixation on building more nuclear weapons will only distract from this technological revolution, making it harder for the United States to master the advances that will shape the battlefield of the future.

NOWHERE TO HIDE

Although the Soviet Union considered using nuclear weapons for warfighting, for decades, nuclear weapons primarily have been seen as instruments of deterrence. These bombs, the thinking goes, are so destructive and invite such uncompromising retaliation that their use in wartime imperils the very existence of the human race. U.S. President Ronald Reagan and Soviet Premier Mikhail Gorbachev captured this idea at a 1985 summit when they declared that “a nuclear war cannot be won and must never be fought.”

But the development of lower-yield warheads and higher-accuracy missiles in the 1980s encouraged some experts to believe that nuclear weapons could become practical tools of war. The debate at that time around so-called neutron weapons stemmed from the notion that such a bomb, accurately delivered, could wipe out an entire tank battalion without killing tens of thousands of civilians.

In the wake of Russia’s invasion, some foreign policy commentators, including New York Times columnist Bret Stephens, have called for the United States to build its own such stockpile—as China and Russia have done. Proponents of the weapons argue that if the United States does not deter these weapons with lower-yield bombs of its own, then China and Russia will take advantage of a “deterrence gap,” using such weapons on the battlefield and then daring Washington to escalate by launching its big strategic missiles against Beijing or Moscow. As the argument goes, the United States will never attack Moscow in response to a small nuclear attack against a German military base. In order to deter the Russians, Washington has to be able to strike them with the same low-yield weapons that they might use in Europe.

The technology revolution is passing nuclear weapons by.

In the 1980s, however, Western publics recoiled against the notion that low-yield strikes were somehow cleaner than larger nuclear weapons. The fact that they would produce little physical damage but would efficiently kill people brought protesters into the streets across Europe and the United States. Faced with this stark reaction, the United States embarked on a long campaign to develop highly accurate conventional weapons, which could effectively retaliate against nuclear attack.

The case for low-yield nuclear weapons will be no easier to make today than in the 1980s, especially since the technology revolution is passing the weapons by. There are limits to further innovation in new nuclear weapons development since one can split the atom in only so many ways. Dialing nuclear yield up or down, increasing or decreasing destructive power—these are all well-understood phenomena that will not change the deterrent balance or make the public more accepting of nuclear use. The same is true of missiles that will deliver nuclear weapons. Since the 1980s, they have become steadily faster and more accurate, and have acquired greater range and maneuverability. Hypersonic weapons are the latest expression of these trends.

These are not the innovations that count today. The most consequential innovations happening now are those that change the environment in which traditional nuclear missile systems must operate. Today, sensor systems on satellites and other platforms are providing ever-sharper imagery and location information for military facilities, weapons, and equipment—day and night, in cloud cover or clear weather. As big data analysis begins to quickly make sense of myriad images and predict changes in them, forces will eventually be able to conduct real-time targeting. Even mobile nuclear missiles and submarines may become subject to such tracking and targeting in the future, as quantum computing and sensing take hold

The implications for nuclear deterrence are stark. All nuclear weapons states have depended on the ability to hide and protect some nuclear missiles so that they would be available to retaliate if somehow an adversary carried out a successful first strike. Such “second-strike retaliatory forces” have been the essential insurance policy that enabled all the nuclear weapons states to feel confident that, even if their adversary surprised them, they would retain the means to respond with nuclear weapons. This retaliatory option is a strong factor in the stability of nuclear deterrence.

With the technology revolution driving in the direction of real-time targeting, however, even the stealthiest or most well-protected mobile weapons will become vulnerable in the future. The day may come when the nuclear weapons states must question the viability of their retaliatory forces because of their vulnerability to attack.

SMART MODERNIZATION

This future threat argues not for abandoning nuclear weapons but for carrying forward a careful modernization of them. As President Barack Obama first said in his Prague speech in April 2009, as long as nuclear weapons exist, the United States must maintain a safe, secure, and effective nuclear arsenal. The modernization program for the nuclear forces of the United States is very much underway and is receiving the funding that it requires. Replacing the submarines, intercontinental ballistic missiles, and bombers will take well over a decade, but the process is vital to ensure that the United States remains secure from nuclear attack during a fraught period of global competition.

In particular, the United States must watch China. China has gone from a nuclear posture depending on a small force of missiles intended for second-strike retaliation to something else. For the past several years, Beijing has been building silos for intercontinental ballistic missiles in its western and northern desert while also building up its warhead numbers. Still, there is no need to panic. Even if it quintuples its stockpile, as some experts are predicting, China’s number of warheads will still be well below the numbers in the U.S. arsenal in 2030.

Washington must remain alert, as well, to what Russia is doing. The country is a highly capable and experienced military nuclear power with a leader whose belligerence is breathtaking. Putin’s nuclear saber-rattling is unlike anything seen in the seven decades since nuclear weapons were last used to attack Hiroshima and Nagasaki at the close of World War II.

The United States will not be the one to launch a nuclear arms race.

But under the New START treaty, both the United States and Russian Federation cannot deploy more than 700 delivery vehicles—missiles and bombers alike—or more than 1,550 warheads. New START remains in force until February 2026. As long as both parties adhere to the treaty, which they have continued to do even during the Ukraine war, the United States will be able to carry out its nuclear modernization in a stable and predictable environment. This predictability is the key reason to replace the treaty before it ends in February 2026: Russia cannot race to build up its strategic nuclear forces while New START limits are in place, as long as the treaty contains a regime that can verify Russia is sticking to its obligations.

China is well below the New START limits today, but if it tries to build up to 700 delivery vehicles and 1,550 deployed warheads, Washington will see it coming with enough time to do something about it. The United States will not be the one to launch a nuclear arms race, but it will respond to others who do.

Secure on the nuclear modernization front, the United States must turn its attention to the technological revolution. China’s intention is to dominate the new technology space. It has the clear goal of being the world leader in artificial intelligence by 2030, and it is putting substantial resources into achieving that objective. Beijing has already put artificial intelligence to work in tightening the security bubble around China’s society and economy, gaining an enormous amount of experience with the technology in the process. If the United States is not careful, China will outrun U.S. artificial intelligence innovation, leading to a dangerous gap in military capabilities. And artificial intelligence is only one arena where China is seeking dominance. The Chinese also have biotechnology, quantum computing, and other sectors in their sights.

Choosing to focus on this technological competition is not easy at a time when the Russian Federation is pounding Ukraine in an unprovoked and unwarranted military invasion. The security of the United States, however, depends on its ability to stay in this race, to compete, and to succeed. The last thing the United States needs, as it is trying to prevail in new technologies, is a nuclear arms race. The wisest choice for Washington, then, is to modernize its nuclear force posture as planned while putting its main emphasis on developing and acquiring new technologies for military applications. A nuclear arms race is a sidetrack that is not in the U.S. national security interest.

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  • ROSE GOTTEMOELLER Steven C. Házy Lecturer at the Center for International Security and Cooperation at Stanford University. She is the former NATO Deputy Secretary-General and U.S. Undersecretary of State for Arms Control and International Security.
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