The views in this paper are the author’s, and should not be construed as representing the opinions of CNA or the Department of the Navy.
Since the Armistice that ended the fighting in Korea in 1953, the U.S.-ROK alliance has been successful in preventing another North Korean invasion. The basic approach has been to present such a formidable defensive posture that the North would never believe it had an opportunity to forcefully reunify the country under its leadership. In other words, North Korea has successfully been deterred. Alliance strategy has worked so well that today the prospect of an attempt by North Korea to militarily reunite the peninsula is judged by many to be incredible. Setting aside the question of whether Pyongyang still has the desire to solve the Korean civil war by force of arms, some argue that North Korea no longer has the capability to invade successfully, even if it wanted to.
Still, both the U.S. and ROK armed forces take the possibility of another invasion, however remote, seriously. The alliance’s Combined Forces Command (CFC) worries about the possibility of a surprise, or short warning attack, because North Korea has positioned much of its Korean People’s Army (KPA) close to the DMZ where it could undertake offensive operations in short order.
Deterrence as Practiced Today in Korea
“Broadly defined, deterrence is the threat of force intended to convince a potential aggressor not to undertake a particular action because the costs will be unacceptable or the probability of success extremely low.” In other words, deterrence comes in two forms—deterrence by punishment and deterrence by denial. In the first instance, potential aggressors are deterred by the prospect of having to endure unacceptable punishment in response to an aggressive act. In the second case, deterrence by denial, the potential aggressor is deterred because defenses are so good that the aggressor concludes that it could not achieve its political and military objectives through use of force. In Korea, the U.S.-ROK alliance combines both of these approaches—a strong defense that can deny success, buttressed with the promise of overwhelming retaliation in the event of an invasion from the north.
For either of these forms of deterrence to be successful what is threatened in response to aggression or a hostile act must be believable, or as it is commonly cast, must be credible. Credibility in turn, derives from a combination of military capability and a belief in the minds of North Korean leaders that the alliance has the political will to act. There is no doubt that the U.S.-ROK allies have the political will to respond to an invasion; hence the conditions necessary for a credible deterrent, capability and political will, are met.
But the North also Deters
History has demonstrated that when it comes to responding to North Korean provocations short of an actual invasion, the circumstances of deterrence have been reversed, even though at every level of war the alliance enjoys a military capability advantage—including the nuclear domain. However, this capability advantage yields no advantage because it has not been buttressed by the perception that the alliance has the political will to act. So far, it has not acted in response to smaller provocations—although that could be changing.
Pyongyang has put in place the capability to deter alliance military responses to provocations by being able to inflict unacceptable consequences on South Korea. Specifically, it has positioned a huge number of artillery pieces and long range rockets close to the DMZ which can fire into Seoul. It is the capability bombard Seoul, to turn it into a “sea of fire” as Pyongyang has put it, that has contributed to Pyongyang’s deterrent against alliance responses to its provocations.
What makes this deterrent credible is the historic willingness of the Kim regime—father and son—to use force in ways that the alliance has perceived as reckless. It has convinced the leadership of the United States and South Korea that the Pyongyang regime might just be willing to unleash an escalatory cycle that could lead to all out war, even though it would probably lose. Pyongyang has created the impression that it does have the political will to act even in ways that appear irrational.
The combination of its conventional military posture plus the perception of a ruthless and reckless leadership has made both the ROK and the U.S. unwilling to retaliate for killing South Koreans (numerous instances) or killing or imprisoning Americans (the 1969 shootdown of an EC-121 reconnaissance plane, the 1976 tree chopping incident, and the 1968 capture of the USS Pueblo). Despite its long history of violent hostile acts against South Koreans and Americans, the alliance has never retaliated to a premeditated violent/hostile act with force. (In December 2010, the ROK military did return artillery fire, in response to North Korea’s shelling of Yeonpyeong Island.) Until very recently, the Alliance has been deterred because of its implicit threat of violence against Seoul, or more broadly because of worries over triggering another war.
Why would Pyongyang wish to continue to execute hostile acts, such as the 2010 sinking of the ROK Navy ship Cheonan and the shelling of Yeonpyeong Island? Decision making in Pyongyang is opaque, and trying to understand the rationale behind North Korean actions is really just speculation. Within the context of deterrence, one (and certainly not the only) possibility is that North Korean leaders understand that periodic violent acts against the alliance serve to reinforce the credibility of North Korea’s conventional deterrent by demonstrating a political willingness to risk war. Perhaps North Korean leaders believe that this advantage has to be periodically reinforced or refreshed by demonstrations that suggest a political willingness to take risks when it comes to the use of force.
Adding the Nuclear Dimension to North Korea’s Deterrent
A KCNA release on April 21, 2010 discussed a North Korean Foreign Ministry memorandum on nuclear weapons. The report includes the statement that, “The mission of the nuclear armed forces of the DPRK is to deter and repulse aggression and attack on the country and the nation till the nuclear weapons are eliminated from the peninsula and the rest of the world. The DPRK has invariably maintained the policy not to use nuclear weapons against non-nuclear states or threaten them with nukes as long as they do not join nuclear weapons states in invading or attacking it.”
If we accept this statement at face value, it sheds some light on North Korean’s perception of how it understands the deterrence dynamic on the peninsula. North Korea sees its nuclear capability as a deterrent against an attempt to overthrow the regime through an invasion. From Pyongyang’s perspective a CFC-led invasion may not seen farfetched. Over the years, the allied war plan in the event of an attack on South Korea from the north (OPLAN 5027) which apparently makes provisions for a North Korean regime change, has been openly discussed or leaked to the press, and we can only guess what information and opinions North Korea has gathered through espionage.
Proactive Deterrence—a New Factor in the Equation?
In the wake of the Cheonan sinking in March 2010, South Korean President Lee Myung-bak announced a new South Korean approach to deterrence called “proactive deterrence.” In a speech to the nation, he indicated that the ROK would no longer depend upon a “passive” deterrent, but instead would retaliate in kind for North Korean provocations. But, this change in the ROK’s declaratory policy did not immediately translate into any new reactions to North Korea provocations, and as a result, may have undercut the new policy in the eyes of Pyongyang because of the cautious and predictable response to the sinking. The alliance response to the Cheonan sinking was a page from its familiar play-book: a call for more sanctions, pressure from the UN, and a show of strength in the form on an alliance exercise.
Proactive deterrence faced another test on November 23, 2010, when North Korea used the pretext of a routine ROK Marine Corps firing exercise to bombard Yeonpyeong Island, killing two ROK marines and two civilians. The Marines did respond with counter battery fire but no further action was taken. Responding to public outrage over this response, President Lee again modified Seoul’s declaratory deterrence policy and explicit rules of engagement by shifting it from “controlled response” to “manifold retaliation.” A month later, in another speech, Lee said, “fear was never helpful in preventing war. If we are firmly determined to brave any risks, we can fend off any emerging threats.”
This change in declaratory policy has potentially profound implications because it signals Pyongyang that Seoul is now equally willing to run the risks and face the possibility of escalation. In the wake of the next challenge from North Korea—and it is a safe bet that one will occur, given the North’s history of provocations and the recent trend—a response that is perceived as proportional and "in kind" would have the best chance of not leading to escalation. But this still entails significant risk, especially if the specific provocation is related to Kim Jong-un, the presumed successor to Kim Jong-il. An orderly succession process is the regime’s current top priority, and anything that is perceived to upset that will not be tolerated.
President Lee’s new policy is courageous, but is also very dangerous because it depends upon the good offices of third parties (e.g. China, Russia) to control escalation if an ROK response triggers a North Korean counter response—which side would be the first to call a halt? It is worth wondering whether, if the passions of the moment in South Korea cool, this new retaliatory policy is politically sustainable. The damage that North Korean long range rockets inflicted on Yeonpyeong was a real-world demonstration of Seoul’s vulnerability—which presumably was at least one reason why the attack was ordered.
What Can the United States Do?
A good point of departure for thinking about the future is the classic adage commonly attributed to the medical profession’s Hippocratic Oath: first, do no harm. This suggests that the U.S.-ROK alliance should carefully reexamine all policy, posture, and command changes that are currently planned or under discussion from the point of view of will the change either increase or undercut deterrence in the eyes of the North Koreans.
In the category of doing no harm, postponing the shift of wartime operational control of ROK forces from U.S. to ROK command until 2015 makes sense. One of the hallowed principles of war is the notion of “unity of command.” A careful reading of military history clearly indicates that this is particularly true when facing a powerful ground threat. It makes little sense to disestablish the unifying command structure in Korea when the threat to the alliance is acting with greater belligerence and improving its military capabilities.
The Idea of Strategic Flexibility
Another related consideration is the issue of what is termed “strategic flexibility” as it relates to U.S. posture in Korea. The concept is intended to characterize the ultimate end state for the U.S. posture on the peninsula, and attempts to mirror the U.S. posture in Japan. In short, the idea expresses the belief that U.S. forces in place for the defense of South Korea could also be employed off the peninsula for other regional contingencies.
Perhaps it is time to reconsider this idea in order to send a signal that the U.S. is not interested in implying by its actions a weakened commitment to the defense of South Korea. Taking strategic flexibility off the table would be a step the alliance could take to impress upon Pyongyang that the defense of South Korea is still its central task, and that the United States is not intimidated by the fact that Pyongyang has a nuclear capability that puts U.S. forces in Korea at risk.
Preparing for a Troubled Future—Going Beyond the Usual Steps
What is needed next are actions that change the deterrent dynamic on the peninsula to one that encourages stability and discourages North Korea adventurism. Hopefully, President Lee’s “manifold retaliation” approach will accomplish that end by promising consequences for hostile acts that go beyond economic and diplomatic options. This means of course that Washington has to be willing to accept the same risks of escalation that Seoul has apparently decided to embrace.
This is not to suggest that the alliance stop taking steps from its tried and true playbook—increasing military presence to show resolve, conducting military exercises to demonstrate and hone military capability, seeking international condemnation through the United Nations, and pressing China to exert more pressure on Pyongyang. These are all important steps to take, but they are the same steps that have been taken over the years with scant lasting effect on Pyongyang’s long-term behavior. It seems obvious that when the Kim regime decides to conduct a hostile act, up to now it has had a good idea of how the alliance and international community will react. Pyongyang has not been deterred by the potential consequences.
To make this new deterrent policy more credible, reducing the vulnerability of Seoul to conventional bombardment is a priority. Seoul’s proximity to the DMZ provides the North with a huge asymmetric advantage. Can this advantage be nullified? Obviously, Seoul cannot be towed a hundred kilometers south, but is it possible to demonstrate to the people of South Korea that the alliance has the ability to defend Seoul effectively against a North Korea bombardment? This tactical issue, which has strategic consequences, is not unique to Korea. The government of Israel is wrestling with a very analogous problem—how to defeat a Hezbollah bombardment without having to invade Southern Lebanon. Israeli initiatives in dealing with this problem should be investigated.
What Role Does Extended Nuclear Deterrence Play in Dealing with Hostile North Korean Acts?
The Obama administration has been attentive to the importance of extended deterrence, the provision of the so-called nuclear umbrella to friends and allies threatened by states like North Korea that possess or are seeking nuclear weapons. Historically, extended deterrence has been based on the combination of the strategic nuclear triad (sea-, air-, and land-based delivery platforms), tactical or non-strategic nuclear weapons permanently stationed abroad, and U.S.-based weapons that could be deployed quickly in the case of emergencies.
Since President George H.W. Bush’s direction, there have been no nuclear weapons in South Korea since the early 1990s. The April 2010 Nuclear Posture Review makes clear, however, that the U.S. depends on,” …the capacity to re-deploy non-strategic systems in East Asia if needed in times of crisis.” These explicit comments in an official statement of U.S. policy are clearly aimed at North Korea. The language is clear: the U.S. has both the capacity and policy in place to reintroduce tactical nuclear weapons to the Korean peninsula, and the aircraft to deliver them, should the situation dictate. This is an important aspect of extended deterrence as it applies to potential North Korean use of a nuclear weapon.
One aspect of America’s evolving extended deterrence doctrine may have only limited salience in South Korea—missile defense. The NPR states, “Effective missile defenses are an essential element of the U.S. commitment to strengthen regional deterrence.” However, the North Korean inventory of short-range missile is very large. Even a robust missile defense system could be overwhelmed, and it would take superb intelligence to be able to determine which missiles are nuclear-tipped and which are not. If it were possible to actually discriminate between the two types of missile loads, missile defense could trump the North’s nuclear threat, and that in turn could have a chilling effect on Pyongyang’s willingness to undertake hostile activities—especially if these steps were taken in conjunction with other steps to lesson the impact of the North’s conventional deterrent.
A final aspect of extended deterrence that could have an impact is in the realm of declaratory policy. It is worth wondering if President Obama’s vision for the eventual elimination of nuclear weapons has raised doubts in Pyongyang regarding the credibility of America’s nuclear umbrella. Does Kim Jong-il doubt that Obama would ever actually direct the use of a nuclear weapon? Does the increasing salience of conventional weapons in America’s extended deterrent suggest to him that a U.S. nuclear response is not credible? Perhaps. One way to strengthen extended deterrence would be to give Pyongyang a dose of it own bloodcurdling rhetoric. President Obama could give a speech explicitly stating that if North Korea ever uses a nuclear weapon against South Korea, the United States will retaliate with a nuclear weapon, and will hunt down and kill or capture Chairman Kim and every member of his national security decision-making team.
Preparing to deal with hostile actions by North Korea is intertwined with deterrence. The cruel irony that the alliance faces is that while it possesses escalation dominance with both conventional and nuclear weapons, it is disadvantaged by geography because of Seoul’s location. This susceptibility to conventional attack combined with Pyongyang’s track record of high risk behavior have, until recently, made the allies reluctant to test the Kim’s willingness to escalate if the alliance retaliates.
Whether this new more aggressive stance will have the desired effect and make Kim Jong-il more risk-averse remains to be seen, as does the willingness of alliance leaders to actually go through with a stronger – and riskier – response to a provocation. What the alliance can do is to continue to employ a full range of diplomatic and economic responses. Nevertheless, so long as these traditional methods do not have whole-hearted support from China the retaliatory effect will be limited. To solve this problem the alliance must somehow persuade Beijing that its security concerns are understood and will not be compromised if actions Beijing takes to punish North Korea destabilize the Kim regime. In other words, the allies should attempt to assuage Beijing’s strategic concerns regarding U.S. presence north of the DMZ. Washington and Seoul can also implement – but should not state – a more negative assurance to China. In response to the shelling of Yeonpyeong Island, for example, the allies conducted drills in the West Sea (or Yellow Sea), which China has warned it considers a sensitive area. These drills were a tangible reminder of the “costs” Beijing assumes because of its tolerant approach to North Korean behavior.
Finally, we should not lose sight of the fact that being reluctant to retaliate and perhaps trigger an escalatory cycle that could lead to war has been a successful strategy against a second North Korean invasion. South Korea has avoided war, and as a result has flourished politically and economically. In retrospect, the frustration of not being able to militarily punish North Korea for its hostile acts has been the price that was paid for the overall success of South Korea and its current prominence in the world. Ironically, by attempting to deter North Korean provocations, the new approach could make war more likely if it turns out that Kim Jong-il has a higher tolerance for risk than President Lee believes. If over time, alliance mangers conclude that restraint is more sensible than retaliation, the North should not be allowed to conclude that this “turning the other cheek” to a hostile act implies a weakness in the ability of the alliance to defeat an invasion.
 Michael S. Gerson, “Conventional Deterrence in the Second Nuclear Age,” Parameters, Quarterly Journal of the U.S. Army War College, Autumn 2009, p. 34.
 At the 2010 Shangri-la Dialogue Secretary of Defense Gates reinforced this point when he indicated that the Obama administration would back Seoul’s approach to the Chenonan sinking, even if the response is less forceful because of the, “...worry about provoking further instability and further provocations from the North.” Cited in the Global Security Newswire story, “South Korea Brings North before the U.N. Security Council,” June 7, 2010, http://gsn.nti.org/gsn/nw_20100607_8852.php.
 Other considerations include revenge/retaliation, providing opportunities for Kim Jong Un to build credibility inside North Korea by being involved in military operations, rationalizing a military first policy by provoking crises, and genuine hatred of the South because of its successes. None of these is mutually exclusive.
 Some might argue that this would not be credible given the fact the Osama bin Laden is still alive—true, but he is living as a hunted man in the wilds of Pakistan, a lifestyle that probably holds little appeal to the Kim family and other North Korean elite.