In a nuclear world, nuclear weapons are needed to deter major attacks, but who should possess these instruments of deterrence? The United States has long been committed to stemming nuclear proliferation by both potential adversaries and friends. Today the challenge of keeping nonnuclear states from going nuclear may be growing, perhaps nowhere quite as much as in northeast Asia.
Andrew Marshall, former head of the U.S. Defense Department’s Office of Net Assessment, which is charged with identifying threats the nation might face in upcoming decades, once wrote that any realistic national security strategy must consider the possibility that efforts to prevent nuclear proliferation will fail. But policymakers, legislators, and publics too often take for granted the nuclear status quo.
Sustaining nonproliferation and extended deterrence—that is, deterring not just an attack upon us but also any on our allies—has never been easy or automatic. Early in the Cold War, for instance, France chose to acquire nuclear capability amid doubts about American promises. One can hardly blame South Korea or Japan for their whispered nuclear desires when they have Kim Jong-un living next door. In the face of North Korea’s nuclear advances and China’s maritime aggressions, those whispers are growing louder.
As a presidential candidate last year, Donald Trump said he’d consider accepting South Korean and Japanese nuclear weapons. But formally endorsing them would be a major strategic departure for the United States, and it is highly unlikely that we would aid in their acquisition. The Pentagon’s forthcoming Nuclear Posture Review seems sure to reaffirm the nation’s strong commitment to extended deterrence and nonproliferation.
Japan and South Korea live in a rough neighborhood, surrounded by increasingly adversarial nuclear-armed states with grudges spanning centuries. China’s strategic capabilities and ambitions are on the rise as it continues to assert questionable claims in the South and East China Seas and elsewhere in the Pacific. Since 2013, Japan has been forced to scramble fighter aircraft over 4,000 times to intercept potential incursions by Russian and Chinese aircraft.
A 2016 Center for Strategic and International Studies report catalogued factors that could lead to a cascade of nuclear proliferation. They included an erosion of U.S. extended deterrence, increasing threats from nuclear-armed adversaries, and the availability of relevant technology and knowledge. Unfortunately, some of these very factors are now evident in northeast Asia.
Last year, North Korea detonated a rather large nuclear weapon, with a yield many times that of the Hiroshima bomb, demonstrated a no-kidding intercontinental ballistic missile, and continued work on perfecting a nuclear missile capable of reaching the U.S. homeland. Allies are again asking the perennial question of American willingness to trade Boston for Berlin or Los Angeles for Taipei if U.S. cities are held hostage. In the absence of strong U.S. leadership, Japan or South Korea could become convinced it is alone.
As Henry Kissinger said on the eve of the 2016 election, “It cannot be that North Korea is the only Korean country in the world that has nuclear weapons, without the South Koreans trying to match it. Nor can it be that Japan will sit there.”
Several South Korean politicians have publicly urged their country to develop nuclear weapons. In 2016, the floor leader of the Saenuri party (which has since been renamed the Liberty Korea party) said, “North Korea has been pointing a gun at our head for years. It’s time we stop defending ourselves with a mere sword and have nuclear weapons to challenge its destructive nuclear weapons.” A former top government adviser told the New York Times last year, “If we don’t respond with our own nuclear deterrence of some kind, our people will live like nuclear hostages.”
This impulse has some domestic backing. One 2016 poll showed that 64 percent of South Koreans support their country’s acquiring nuclear arms. Another from September 2017 found that 68 percent of South Koreans support the reintroduction of U.S. nonstrategic nuclear weapons onto the peninsula. The Liberty Korea party has adopted a platform calling for just that. A more cautious statement came from the current defense minister, in the ruling center-left Korean Democratic party, who said, “The redeployment of tactical nuclear weapons is an alternative worth a full review.”
Even if South Korea were to request such weapons, it is far from clear that the United States would provide them. Among other things, storing such weapons farther away from the likely theater of conflict makes them more secure and less subject to preemptive attack. But then the question recurs whether weapons a world away would really be wielded. The perceived value of forward deployment is partly why the United States still keeps a modest number of nuclear gravity bombs at several sites in Europe.
The Japanese government has long been vocal in support of nonproliferation, and public opinion remains strongly against nuclearization. Yet Japan has already quietly acquired a sort of nuclear hedge.
Japan has one of the largest nuclear industries in the world, with stockpiled nuclear material sufficient for many hundreds of weapons. In short, Japan has what the United States and others have worked to keep from Iran—the ability to “break out” and acquire nuclear weapons in a short period of time. Some commentators count Japan as a de facto or virtual nuclear power.
Japan’s status as the world’s only victim of a nuclear attack and its nonbelligerent constitution provide major cultural barriers to nuclearization. But this could change, either through gradual evolution or with sufficient strategic shock. Already the proposed growth and improvement of conventional military forces enjoys deep support. Coming off a huge electoral victory in October, Prime Minister Shinzo Abe may seek a reinterpretation of Japan’s constitution that would allow further expansion of its conventional military forces.
So what would a more proliferated world be like? It could be quite anarchic. Instead of being the primary security guarantor and enforcer of a rule-based global order, the United States might assume a very different role. The international order could be more sharply characterized by spheres of influence, brutal power politics, brinksmanship, and greater instability.
More nuclear powers means a multiplication of the number of deterrence relationships, creating more chances for miscalculation. On one hand, power disparities would remain, so states like China or Russia might be tempted to press their interests against smaller nuclear states. On the other hand, the belief of a smaller power that nuclear weapons bring “automatic deterrence” could send it blundering into conflicts it couldn’t win.
In a crowded nuclear world, strategic stability would require more of the ever-elusive understanding of one another’s intentions, red lines, and core interests. Does China truly know the lengths to which Japan would go to maintain its control of the Senkaku Islands (near Taiwan), which China considers its own? Does Japan understand how far China would press its claims to those islands? Does either know the circumstances in which America would intervene on
Japan’s behalf? Clear communication is critical to avoiding misperception and doubt. The administration’s recent National Security Strategy (released in December) and National Defense Strategy (released in January) presented a realistic rearticulation of America’s role in a world characterized by great power conflict, as well as a blunt list of core national security interests.
To preclude further proliferation in the Asia-Pacific region, at least three lines of effort, all briefly touched on in these documents, should be pursued: modernizing the U.S. nuclear force, boosting allied strike and missile-defense capabilities, and improving military integration. If we want to keep our allies convinced that they do not need their own nuclear weapons, we must ensure they have faith in ours. At a minimum, this means continuing the nuclear-modernization efforts begun during the Obama administration. All three legs of the triad (nuclear-armed submarines, bombers, and ICBMs) are in desperate need of recapitalization, and putting it off further is no longer an option. Indeed, additional adjustments may be required.
Press reports suggest that the Nuclear Posture Review, expected out this week, will recommend modifying current systems and reviving old capabilities, such as developing nuclear weapons with lower yields and restoring the sea-launched cruise missile capability that was formally retired in 2013. Both would contribute to boosting U.S. flexibility and credibility. Continued deterrence dialogues with allies are also essential, so that they understand some details of U.S. capabilities and appreciate the intensity of U.S. resolve.
A second priority should be building partner capacity for conventional strike and missile defense. Missile defenses fielded by Japan and South Korea remain quite few in number, but several signs point to the prospect of serious expansion. Continued Patriot and THAAD (Terminal High Altitude Area Defense) deployments as well as the introduction of several Aegis Ashore sites in Japan, with a more diversified set of missiles than those at the Aegis Ashore site in Romania, would go a long way here. In addition to F-35 stealth fighters, allies like Japan and Australia (and those in other regions, such as Poland) might acquire long-range Tomahawk cruise missiles for deterrence and even preemptive self-defense. In the cooperative development program for the latest version of the Standard Missile-3 missile defense interceptor, Japan’s work on the booster has enhanced industrial skills that could be redirected to other purposes, such as developing ballistic or cruise missiles of its own. South Korea, too, must continue to expand its strike capability in the form of ballistic and cruise missiles. Each time North Korea launched an ICBM last year, South Korea launched its own salvo of missiles into the sea within minutes, demonstrating its alert status and readiness to respond in an actual crisis. The Pentagon’s forthcoming Missile Defense Review will presumably consider how partner capacity can help counter the full suite of missile threats.
A third path involves tighter military cooperation and integration. Improved information-sharing and a single common picture tracking all airborne objects would make the combination of military forces more effective while allowing each to retain separate and distinct sovereign command and control. South Korea appears to have agreed recently to severely limit missile-defense cooperation with America in exchange for normalizing relations with China following a yearlong spat over THAAD. Such concessions could prove deeply problematic. If assurance is to be improved with conventional forces, the watchword should be more integration, not less.
It’s unlikely that South Korea or Japan will go nuclear anytime soon—assuming that the regional security situation remains more or less constant. The leadership of both countries have repeatedly rejected nuclear acquisition, and the potential blowback of any change in this policy would weigh heavily on political and economic interests. If its bullying reaction to the limited THAAD deployment is any indicator—boycotts, travel restrictions, hacking of government websites—China might impose massive economic and military coercion to preclude a nuclear newcomer.
Nevertheless, national survival is the factor that could lead states to pay all those costs and more. Global nonproliferation efforts over the years have thus far been successful in keeping all but the most determined nations nonnuclear—which is to say they have worked, except when they haven’t. A more highly proliferated world is not desirable, but it is conceivable.
Thomas Karako is a senior fellow in the international security program at the Center for Strategic and International Studies.
