It has been quite a summer in Pyongyang. Between July 4th, when it tested its first ICBM, and Labor Day weekend, when it detonated its sixth nuclear bomb — possibly a thermonuclear weapon — North Korea has presented the United States and the world with a new strategic reality. Pyongyang can use long-range missiles to reach almost any location in the United States, and likely has several dozen warheads. If it hasn’t fully miniaturized its nuclear capability yet, it is right on the cusp. And if its sixth nuclear test isn’t an H-bomb, it is least a boosted-fission weapon with the ability to devastate major cities. Observers should not cling hopefully to news of failed re-entry vehicles — North Korea is no longer a risible, rag-tag nuclear aspirant. For all intents and purposes, Pyongyang can hold much of the continental United States at risk and has functionally achieved a second-strike nuclear capability.
The reality is, however, that this new strategic picture has been coming into focus for quite a while. For several years, U.S. officials have watched Pyongyang speed up its nuclear developments and known that a preventive strike against North Korea could result in devastating retaliation within the region. Arguably the most significant strategic implication of North Korea’s technical achievements this summer is not the magnitude of the nuclear threat posed by Pyongyang, but the political consequences for U.S. alliances in Asia. Several countries in the region, notably South Korea and Japan, rely on extended deterrence, or the so-called U.S. “nuclear umbrella,” for their security. Through mutual defense treaties, Washington has promised to treat an attack on Seoul or Tokyo as a threat to its own security, and to respond swiftly to aggression against these allies.
The trouble is, the United States has far less incentive to intervene on behalf of South Korea or Japan if North Korea can respond with a nuclear strike against the U.S. homeland. This phenomenon, whereby a nuclear-armed adversary can separate a security guarantor from its ally, is known as “decoupling,” and provoked angst in the NATO alliance for much of the 1960s. When the Soviet Union gained the ability to hit the United States with nuclear weapons, U.S. policymakers crafted military and diplomatic approaches to convince European allies that they could still depend on U.S. extended deterrence. That allied assurance campaign paid off, allowing NATO to deter the Soviet Union in a coordinated and coherent manner, and preventing some states from seeking nuclear weapons of their own.
Few of the assurance strategies the United States used with NATO are available for contemporary Asia, however, because America’s Asian alliances are different in their structure and relationship to nuclear weapons, and because of the uncommon diplomatic proclivities of the Trump administration. U.S. officials will have to develop new initiatives – while relying on familiar resources – to keep Pyongyang from driving a wedge between the United States and its allies and undermining regional security in Asia.
An Extended Deterrence Refresher
When a country like the United States extends deterrence on behalf of an ally, it assumes a considerable strategic burden. As Thomas Schelling argued, it is perfectly believable to tell an adversary that you will retaliate against an attack on your homeland, but making the same promise on behalf of an ally is fundamentally less credible: Why should an aggressor accept that you will treat another state’s sovereign territory as your own? Over the years, the United States has developed a litany of military and diplomatic approaches to demonstrate that its security fate is tightly coupled with those of its allies: forward deploying troops, engaging in joint training exercises, and reiterating the U.S. treaty commitment at times of peace and crisis. Washington employed these signals of commitment in Asia for decades with good success. Now, North Korea has changed America’s ability and incentive to do this.
Before North Korean missiles could reach U.S. territory, the United States could promise to defend South Korea or Japan using all means at its disposal — including nuclear weapons —without worrying that Pyongyang could retaliate against the U.S. homeland. To be sure, this promise entailed great risk even before this summer: Any war on the Korean Peninsula would imperil the lives of 28,500 U.S. servicemembers and their families as well as the 120,000 American civilians who live near Seoul. With its long-range missiles and sophisticated nuclear weapons, however, North Korea has significantly raised the costs of keeping U.S. commitments, as it can now devastate entire American cities if the United States defends its allies. Put differently, North Korea has forced the United States to reckon with whether it would trade San Francisco for Seoul.
This makes it harder to deter North Korea, and harder still to convince South Korea or Japan that the United States will do so. This dilemma only serves North Korea’s interests: It can more effectively intimidate Tokyo and Seoul if it can convince them that the United States will not aid them, and it would love nothing more than to erode U.S. security guarantees over time. For a security guarantor, this is a vexing strategic bind, and the consequences of mismanaging it include poorly coordinated defense and deterrence, regional arms racing, and nuclear proliferation. It is not, however, entirely without historical precedent.
U.S. strategists first wrestled with alliance decoupling in the late 1950s and early 1960s, when the Soviet Union acquired ICBMs and a reliable second-strike capability. As it crossed these technological thresholds, European partners knew that American promises to defend Berlin from a conventional ground invasion would be attenuated if Moscow could devastate American cities in response. At the time, the United States was conventionally inferior to the Soviet Union in Europe and heavily reliant on its nuclear arsenal to uphold its guarantee to NATO. Holding NATO together despite this strategic shift became something of a passion project for Secretary of Defense Robert McNamara.
First, McNamara announced a doctrine of Flexible Response, adopted by NATO in 1967, which aimed to give the alliance more conventional military options for warfighting below the nuclear threshold. By claiming it could credibly fight a conventional war in Europe, the United States at least somewhat mitigated European worries that it would not trade New York for Berlin.
Second, officials in the Eisenhower and Kennedy administrations considered establishing a multilateral nuclear force for NATO. If NATO had its own dedicated nuclear forces, rather than relying on the United States to backstop its security, it could more credibly threaten to use those weapons without placing the U.S. homeland at direct risk. The Multilateral Nuclear Force proposals raised as many problems as solutions, and were soon set aside. In their place, McNamara suggested a Nuclear Planning Group — an institution within NATO that exercised some oversight of nuclear weapons in Europe. NATO embraced the proposal, and the new body gave allies a sense of control over their collective nuclear fates. By involving allies in planning for NATO nuclear operations and strategy, the Nuclear Planning Group convinced Europeans that the American arsenal could not be separated from the fate of the continent. There was an illusory element to this, however: Only a small fraction of nuclear weapons in Europe were governed by the institution, with most remaining under the exclusive control of the United States.
Nevertheless, McNamara’s assurance onslaught preserved NATO during a tenuous time. Although France built its own nuclear arsenal and left the NATO military structure in 1966, it had acquired its weapons before Kennedy took office. In no small part due to Flexible Response, the Nuclear Planning Group, and careful alliance management, West Germany abandoned its own nuclear quest and other allies were eventually convinced that the United States would not allow itself to be dislodged from Europe.
The Risks of Decoupling in Asia
As with the Soviet Union and NATO, a sophisticated North Korean nuclear weapons and ICBM capability means the United States will have to work to convince its allies that it still intends to defend them. If Washington allows itself to be separated from Seoul and Tokyo, South Korea and Japan will have incentives to pursue independent military capabilities and policies. This could lead to regional arms racing and, perhaps, to South Korea and Japan acquiring nuclear weapons of their own. Seoul and Tokyo will be less inclined to coordinate regional defense policy with the United States which would, in turn, undermine efforts to deter and contain North Korea, as well as regional defense posture more broadly. Over time, this would seriously erode America’s position in Asia. But U.S. policymakers do not have the luxury of simply dusting off McNamara’s playbook.
First, the United States has no single multilateral alliance in Asia, but rather a series of bilateral pacts. There is a host of historical reasons for this, but this “hub and spokes” structure means there will be no single doctrinal or institutional solution to the decoupling dilemma. Japan and South Korea have a historical rivalry, and while they have made significant strides in recent years, their relationship cooled in late 2016 and has not been revived since President Moon Jae-in was elected in South Korea. Even if trilateral cooperation is fully restored, the lack of a single allied military command means there is no “Flexible Response”-like analogue. The United States does not have a combined command with Japan, and while it could revise its military doctrine with South Korea, that alliance is already conventionally superior to Pyongyang. A single, conventional alliance warfighting doctrine will not solve this problem.
Second, the United States cannot use theater, or tactical, nuclear weapons for allied assurance in Asia. Since the Cold War, the role of these weapons in U.S. strategy has changed. Washington deemed its theater nuclear weapons redundant and withdrew them from Asia after the fall of the Soviet Union. Returning them would be unwise. Theater nuclear weapons hold no military advantages over the U.S. strategic nuclear triad of ICBMs, SLBMs, and bombers, which are now all extremely accurate over long distances, and may instead act as destabilizing targets for first strikes. As a result, however, the United States cannot create a Nuclear Planning Group-like institution to give South Korea and Japan some semblance of nuclear control.
Third, and relatedly, North Korea is a different adversary than the Soviet Union was, and the requirements for deterring it are distinct. The lack of nuclear weapons in Asia makes it more likely that the United States will rely on shows of force and demonstrations with other weapons platforms. Washington must be cautious with the signals it chooses to send, however, because most analysts believe the Kim regime has sought nuclear weapons to guarantee its survival. Kim Jong Un might be willing to use these weapons first if he believes his survival or the survival of his regime is at stake. It may be tempting to the United States to demonstrate its commitment to allies through shows of force and military exercises using heavy bombers and fifth-generation fighters, but planners must keep Kim’s decapitation fears front of mind. Washington must balance any benefits of those assurance attempts against the risks of serious instability that may arise if Kim misinterprets exercises as attacks.
In Cold War Europe, the United States used nuclear weapons to compensate for conventional inferiority and to deter the Soviet Union from taking new territory. U.S. military power was used to keep the Soviet Union out of Western Europe, and while its purposes on the Korean Peninsula today are still fundamentally defensive, Kim Jong Un may not see it that way. If he doesn’t, deterrent signals could quickly become catastrophe. And these are the constraints that have nothing to do with the current U.S. administration.
This summer, the Trump administration’s approach to North Korea has been the stuff of Pyongyang’s wildest decoupling dreams. The president has made apocalyptic statements suggesting the first use of force against North Korea without consulting with allies, and has repeatedly contradicted his own cabinet officials when they try to qualify his remarks. In statements censuring North Korea for its provocative behavior, Donald Trump routinely fails to mention U.S. allies, leading them to worry they have been abandoned on the front lines. This is not misplaced anxiety: A U.S. senator has insisted that Trump sees regional security as entirely distinct from the safety of the American homeland. Further, in an utterly perplexing move, Trump threatened to end the South Korean-U.S. free trade deal in the midst of North Korea’s technological triumphs, holding at risk the economic ballast of the alliance at a harrowing moment. Trump previously threatened to force South Korea to pay for THAAD, and coupled his most recent trade warning with a tweet accusing South Korea of appeasement towards the North. What’s more, the administration has yet to appoint the ambassadors or senior Department of State or Department of Defense officials who are responsible for working closely with allies on sensitive security matters.
In response, Moon has actively distanced himself from Trump, making it clear that he will not be dragged into a reckless war that Washington starts, and public opinion of the United States is plummeting in South Korea. The president has not only failed to mount an active reassurance campaign; he has himself carved the rift into which Pyongyang will drive its wedge. This was likely a leading objective in North Korea’s late August missile launch over Japan, and it will use future threats and tests to try to reveal the United States as a flimsy security patron. North Korea has long hoped to convince the South that the United States will not defend it, as this may allow it to coerce and intimidate Seoul in new and harrowing ways. With his alliance malpractice, Trump is playing directly into Pyongyang’s hands.
Defense Against Decoupling
When it comes to North Korea strategy, there is rarely good news, but alliance management is one area where all is not lost — yet. If the Trump administration decides to defend its Asian alliances against decoupling, it can make progress quickly using many familiar tools. More than any single proposal, the Kennedy and Johnson administrations expended copious diplomatic energy to hold NATO together, appointing top officials to European postings and making the alliance a priority for the State and Defense Departments. If the United States intends to contain and deter North Korea — there is little chance of doing much else at this stage — competent alliance management is essential.
The administration must immediately nominate assistant secretaries of state and defense for Asia as well as an ambassador to Seoul, and these new officials should make swift trips to the region to meet with their counterparts. Second, it should continue and elevate the extended deterrence dialogues with South Korea and Japan that were established during the Obama administration to engage in strategic planning and exercises. These dialogues have continued since Trump took office, but with no political appointees in place they cannot serve their intended purpose. They should be raised to the assistant or deputy secretary level as a sign of their strategic import (and the names can easily be changed if the Trump team wishes to create political distance from an Obama accomplishment). With these officials in place and dialogues revived, the administration should double down on its efforts to build the trilateral relationship with Tokyo and Seoul. Although the three nations lack a single set of alliance institutions, intelligence sharing and missile defense cooperation could eventually play similar roles – but this will require a substantial diplomatic investment from Washington. Fourth and finally, the administration must articulate clear objectives for its North Korea strategy and be plain about the role that allies play in its declaratory policy. Even if the Trump team takes all of the other steps, so long as the president continues to threaten allies and contradict his cabinet, he will undercut any progress that is made.
Nuclear strategists are fond of saying that allied assurance is harder to achieve than deterrence. Deterrence requires the United States to influence North Korea’s willingness to attack, but assurance also requires it to convince its allies that it is has accomplished this effectively, with their security dependent on these U.S. guarantees. This is no easy feat, and yet decoupling fears are as old as ICBMs themselves. While McNamara’s playbook may not hold all the answers, some progress can be made through the concerted application of diplomatic will. Of late, this has been in devastatingly short supply, but if ever there were a time to summon it, it is at the end of North Korea’s nuclear summer.
Mira Rapp-Hooper is a Senior Fellow at the Paul Tsai China Center at Yale Law School and an Adjunct Senior Fellow at the Center for a New American Security. She writes and researches on national security in Asia and is currently writing a book on the role of alliances in U.S. foreign policy since 1945.