The US Doesn’t Need to Worry About Japan (or Any Other Ally) Going Nuclear

U.S. President Joe Biden will need to take a number of steps to restore allied confidence in the United States. Strengthening the U.S. nuclear umbrella isn’t one of them.

That’s not how many experts see it. They’re going to tell Biden that terrified allies need immediate reassurance the United States will defend them with specially tailored nuclear options. They’ll claim these options require developing new types of nuclear weapons and threatening to use them first in a conflict. And they’ll claim these allies will build their own nuclear weapons if he refuses to follow their advice.

That, as Biden might say, is a bunch of malarkey.

The Nuclear Umbrella

At the dawn of the nuclear age, to encourage friendly countries to refrain from building nuclear weapons, the United States promised to protect them with U.S. nuclear weapons. This arrangement came to be called the nuclear umbrella. The experts call it extended nuclear deterrence.

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The umbrella covers the countries in the North Atlantic Treaty Organization (NATO), Japan, South Korea, and Australia. It is not a binding legal arrangement included in their security treaties with the United States. It is an informal assurance reinforced by dialogue and, in the case of NATO, cooperative arrangements to deliver U.S. nuclear weapons if authorized by a U.S. president.

Whether the umbrella is the only reason these nations did not build nuclear weapons, or even the most important reason, is difficult to know. Doubts about the efficacy of nuclear weapons, moral reservations, public opposition, and other factors also influenced allied decisions. Today, all of the so-called “umbrella states” are members of the Nuclear Non-Proliferation Treaty (NPT) and bound by that treaty to remain non-nuclear.

How It Works

An umbrella is a simple device. So is the nuclear umbrella. Many non-nuclear countries don’t think much about nuclear weapons. Some have established nuclear weapons-free zones. But a small group of non-nuclear U.S. allies fear they might be attacked with nuclear weapons. The United States reassures these allies by promising that if they are attacked with nuclear weapons, it will retaliate with nuclear weapons on their behalf. The hope – and it is just a hope – is that this promise of retaliation will prevent an attack.

Umbrellas can’t keep us completely dry in the rain, especially during a storm. And the nuclear umbrella can’t completely eliminate the fears of U.S. allies. It’s just a promise, and it’s impossible for the United States to guarantee that promise will prevent an attack. Enemies may wonder if the United States will keep that promise, especially since to honor it the United States must risk its own destruction. It is natural for U.S. allies to wonder if a U.S. president would, if the time came, be willing to take that risk.

Allied doubts are not about whether the U.S. military can retaliate. The nuclear umbrella is mechanically sound. The United States has many different kinds of nuclear weapons it can reliably deliver to targets anywhere in the world. It doesn’t need more.

The question is whether the United States will retaliate. No one can know for sure.

A Question of Trust

In 2009, while the Obama administration was conducting its nuclear posture review, a political officer in the Japanese embassy invited me to lunch to talk about China. This same diplomat would go on to lead the first series of U.S.-Japan dialogues on extended deterrence and become the vice minister of foreign affairs.

He began our conversation by asking, “If you were responsible for the defense of your country and you had to depend on somebody from another country, how would you feel?”

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It’s a good question. He ended the conversation by telling me the only cooperative nuclear arrangement that would satisfy him would be for the United States to supply Japan with U.S. nuclear weapons, train the Japanese military to deliver them, and give the Japanese government the authority to decide how and when they will be used.

That suggests that particular diplomat has a very low level of trust in the U.S. nuclear umbrella. There has always been a handful of defense and foreign policy bureaucrats in every umbrella country who think the same way. Yet, their governments still rely on the U.S. umbrella and remain in the NPT.

U.S. experts will tell President Biden, as they have told his predecessors, that they remain because the United States successfully coddles fearful bureaucrats by providing specially tailored U.S. nuclear options they can ostentatiously practice exercising every now and then.

But these kinds of half measures can never completely relieve the anxiety of any allied defense official who harbors the very reasonable suspicion that a U.S. president might not authorize the use any of those options if it risks a nuclear attack on the United States.

An important question for Biden is whether those suspicions have now grown so large that U.S. allies will finally quit the NPT to build their own nuclear weapons.

Proliferation Risks?

Will Japan, Germany, or Canada be the next North Korea? The NPT allows member states to withdraw from the treaty if “extraordinary events” threaten their “supreme interests.” A Biden administration decision to cancel a new submarine launched cruise missile or declare that the United States will not use nuclear weapons first are not the kinds of events the authors of the treaty had in mind.

There’s very little chance Japan or any other umbrella state would quit the NPT in response to any change in U.S. nuclear weapons policy. Japanese defense experts concluded, twice, in 1968 before joining the NPT and in 1995 before agreeing to a permanent extension of the treaty, that “the nuclear option is not a favorable one.” Japan and many other U.S. allies still feel the same way.

But the most important reason allied bureaucrats will not urge their governments to build nuclear weapons – at least not publicly – is because they know they would lose their jobs if they did. It is not a politically acceptable idea. Anti-nuclear norms are strong among voters in Japan and many other umbrella states.

It is those norms, reinforced by the legal constraints of the NPT, and not U.S. appeasement of a handful of jittery allied bureaucrats, that keeps umbrella states from building their own nuclear weapons.

Moreover, the entry into force of the Treaty on the Prohibition of Nuclear Weapons (TPNW) will increase public pressure on umbrella state governments to demonstrate their commitment to nuclear disarmament. If Biden ignores that pressure and subordinates progress on nuclear arms control to the insatiable demands of a few allied defense officials, some allied governments may be compelled to give in to public pressure, discard the U.S. nuclear umbrella, and join the TPNW.

Biden should keep that in mind as he reconsiders U.S. nuclear weapons policies. He can forgo first use options and cut back on nuclear weapons spending confident that no U.S. ally will become the next North Korea.

Gregory Kulacki, Ph.D., is a senior analyst with the Global Security Program of the Union of Concerned Scientists.

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