North Korea's successful launch of a long-range rocket, its third nuclear test, and threats to follow up with even "stronger steps" and the "final destruction" of South Korea are raising serious questions among America's Northeast Asian allies. So is China's growing assertiveness over the Senkaku/Diaoyu Islands in the East China Sea. The most fundamental question is this: is US extended deterrence failing?
The short answer is no. US extended deterrence, which underpins America's alliances with South Korea and Japan, is working well. Its boundaries, however, are being dangerously tested, which demands urgent improvement of alliance coordination and cooperation.
Extended deterrence (ED) is a by-product of deterrence. Deterrence means preventing aggression or coercion against
one's vital interests by threatening to defeat or punish an adversary; although it has been mainly conducted with nuclear threats, non-nuclear capabilities have played a greater role over time, particularly missile defense, counterforce assets, and advanced conventional weaponry. ED simply means providing the same level of protection to an ally, with the same deterrent threats. To work, therefore, ED requires the United States to deter its allies' adversaries and to assure its allies that it has the capabilities and intentions to do so. That is why ED is said to have both deterrence and assurance missions.
Successful deterrence of adversaries can only be measured in the negative: the absence of aggression against US allies' vital interests suggests that deterrence works. Successful assurance of allies is more difficult to measure because it depends on numerous variables. A key indicator of success, however, is allies' readiness to forego certain capabilities, notably nuclear weapons, and rely instead on their US ally to provide them.
Some argue that North Korea's nuclear and missile developments means that deterrence of Pyongyang is failing. They point to the North Korean provocations of 2010, notably the sinking of the Cheonan, a South Korean corvette, and the shelling of Yeonpyeong Island, as proof.
This is misleading and a mistake. Since the Korean Armistice Agreement that ended the fighting on the Peninsula in 1953, North Korea has been deterred from conducting another invasion of the South. ED has been so successful that an invasion appears inconceivable today. Similarly, leaders in Pyongyang know that launching a massive, let alone nuclear, strike campaign on Seoul or Tokyo would be suicidal. Again, ED has kept them in check.
Granted, ED has not prevented the provocations of 2010 (and others before that), but it is a mistake to expect it to prevent low-level attacks. Remember, ED is meant to prevent aggression against allies' vital interests. Of course, as its nuclear and missile capabilities improve, there is a risk that Pyongyang feels increasingly confident that it can launch low-level attacks and control escalation.
This is worrisome because escalation control is never guaranteed and misunderstandings, miscalculations, and mistakes are always possible. The good news, however, is that even this dynamic suggests that ED works. Although its boundaries are being tested, it still deters major conflicts that challenge US allies' vital interests.
Should we understand China's growing military confidence and adventurism in the East China Sea in the same light? Are the effects of China's conventional and nuclear force modernization, notably its growing anti-access and area-denial capabilities, undermining ED? Or are they merely creating low-level conflicts well below the ED threshold?
So far, tensions have increased, but no conflict has broken out. As in the North Korean context, China's probing is a test for ED. Although low-level conflicts are always possible, ED is likely to function because Beijing knows that seizure of the Japanese-administered Senkaku/Diaoyu Islands, which fall under the scope of a US-Japan Treaty of Mutual Cooperation and Security, would trigger a response from Washington.
This analysis points to an important conclusion: by and large, the deterrence mission of ED is working in Northeast Asia. Paradoxically, however, assurance of US allies appears to be faltering.
Both Seoul and Tokyo have doubts about the reliability of ED. In response, they have formulated their respective "Proactive Deterrence" and "Dynamic Defense" doctrines to enhance their defense capabilities, and there are questions how these doctrines can be properly integrated with ED. Moreover, in the aftermath of Pyongyang's recent missile and nuclear tests, there is a growing clamor in both countries for development of offensive/preemptive strike options to take out the North's key military assets. In South Korea, this complements calls for development of indigenous nuclear weapon capabilities; some have also argued for the reintroduction of US tactical nuclear weapons on the Peninsula.
Likewise, the Japanese are very concerned by China's assertiveness over the Senkaku/Diaoyu Islands, insisting that Beijing is testing the US-Japan alliance. At the recent Pacific Forum CSIS annual US-Japan Strategic Dialogue, one Japanese indicated that failing to respond appropriately could set a bad precedent for the territorial disputes in the South China Sea.
More generally, despite the US "rebalance" to Asia and stated commitment to strengthen ED, South Korea and Japan remain skeptical about its reliability and sustainability because of US fiscal constraints and commitments elsewhere in the world. At issue is also the US decision to reduce the roles and numbers of nuclear weapons in its national security strategy, which both Seoul and Tokyo regard with concern when it comes to ED.
More reassurance of South Korea and Japan is urgently required. Beyond public statements re-emphasizing US commitment to their defense (which US President Barack Obama has made), the United States should work through the bilateral ED consultative mechanisms it has established with South Korea and Japan to enhance alliance coordination and cooperation and eliminate their growing perceived need for independent nuclear weapon capabilities.
With the emergence and possible multiplication of low-level attacks or provocations, critical questions need to be answered about the roles, missions, and capabilities of US allies and of the United States to better prevent and respond to a conflict as it develops and, particularly, as it escalates from a low-level to a mid-level and higher-level, until ED kicks in. The United States also needs to discuss with its allies how ED works along a spectrum, with the use of nuclear weapon at the far end of this spectrum.
US allies often call for Washington to make specific commitments and share detailed plans on how it would respond to incidents. More sharing may be necessary to enhance allies' assurance, and it will probably be unavoidable when the United States transfers wartime operational control to South Korea in December 2015. Yet, it is unrealistic for allies to expect the United States to abandon all ambiguity about its intentions because of fears of reducing US flexibility of responding in a crisis.
Alliance coordination, therefore, is best enhanced through regular consultations and dialogues, both at the political and operational levels, and through joint military planning and exercises. Both processes are important because they create habits of working together and help to enhance mutual understandings of priorities, requirements, and hurdles.
In the case of North Korea, Washington must also make clear to its allies (and the world) that its determination to better deter and prepare for contingencies against Pyongyang does not mean that it has abandoned the goal of denuclearizing the Korean Peninsula. Refusing to accept a nuclear North Korea is key because allies seek more reassurance than US commitments to their defense, however strong they may be.
Finally, sooner rather than later, trilateral policy coordination among the United States, South Korea, and Japan will become crucial because Seoul and Tokyo have different expectations of Washington. Both are deeply worried about North Korea and their expectations of Washington may (note: "may") align in the event of a contingency. They have different threat perceptions when it comes to China, however. The row over the Senkaku/Diaoyu Islands is mostly of concern to Japanese; South Koreans are indifferent, except as it relates to their claim to the Takeshima/Dokdo Islands. This suggests that should a conflict break out, Tokyo would expect a US response that Seoul might not welcome, hence the need for greater coordination among the Three.
Historical and territorial issues between South Korea and Japan have so far prevented the development of a comprehensive trilateral dialogue. Yet, "functional" trilateral cooperation on ED should be seriously considered because of its potential to enhance reassurance.
In the late 1960s, British defense minister Denis Healey famously stated that it took "only 5% credibility of American retaliation to deter the Russians, but 95% credibility to reassure the Europeans." Even though today's threats are considerably less serious than during the Cold War, the "Healey Theorem" remains valid: the challenges of assurance are much greater than the challenges of deterrence. They can be met, however, if the United States and its allies keep a cool head and work together to enhance high-profile coordination and cooperation.
David Santoro (David@pacforum.org) is a senior fellow for Nonproliferation and Disarmament at the Pacific Forum CSIS.
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