With a fifth nuclear test and repeated ballistic missile launches, North Korea’s provocations appear to be escalating to a new level. Several military exercises and flyovers by U.S. strategic bombers over the Korean Peninsula after nuclear or missile tests may offer meaningful reassurance to allies. But they have not deterred North Korea’s provocations. Given this, the United States and its allies need to review and reconstruct their multi-layered deterrence strategy.
Any such strategy must start with the North Korean leadership’s strategic thinking and threat perceptions. During the Korean War, Japan was the logistical forward base for U.S. intervention on the Korean Peninsula. If a contingency were to arise on the peninsula, the United States would once again rely on Japan. The Korean Peninsula and Japan have been a single-integrated operational theater since hostilities broke out in 1950. The U.S.-Japan defense guidelines and Japan’s new security legislation provide clear evidence of support under these circumstances.
Using its nuclear and missile capabilities, North Korea has threatened Japan with the intention of reducing public support for seemingly “antagonistic” U.S. forward bases in Japan. In fact, the four ballistic missiles fired on March 6 were launched by the Hwasong ballistic missile division, which, according to the Korean Central News Agency, is “tasked to strike the bases of the U.S. imperialist aggressor forces in Japan.” Furthermore, North Korea continues to seek reliable ICBMs so it can threaten nuclear strikes on the United States as a decoupling strategy.
Given all this, how should the United States and its allies respond? Although the seriousness of the conversation is different in Japan and South Korea, one option is nuclear-arming, or the introduction of nuclear weapons by the United States. However, it would seem to be premature to conclude that Japan and South Korea need to develop their own nuclear weapons because North Korea’s nuclear and missile developments are not a failure of nuclear extended deterrence.
For a similar reason, the introduction of U.S. nuclear weapons in South Korea or Japan is not an effective option. Under the current U.S. nuclear posture, there is no way to introduce nuclear weapons other than to deploy B-61 nuclear bombs that can be delivered by dual-capable aircraft (DCAs). However, if there were deployed in South Korea or Japan, they would be vulnerable to a North Korean first strike and therefore would not be an effective deterrent.
Allied governments need to understand the utility and limitations of nuclear deterrence, and explain them to their citizens. But more fundamentally, there are other conventional military capabilities that will contribute more to the defense from North Korea’s missile threats.
Some experts have suggested that the United States consider a preemptive strike to eliminate North Korea’s nuclear and missile facilities, arguing that this is necessary before North Korea obtains a reliable nuclear ICBM. But it would be hard to eliminate North Korea’s survivable road-mobile ballistic missiles targeting Japan, and substantial artillery batteries targeting Seoul.
Some Japanese lawmakers are pushing for Japan to develop its own strike options. At the end of March, Japan’s ruling Liberal Democratic Party (LDP) study group – comprised mostly of former defense ministers – submitted a recommendation for acquiring “counter-attack capability.” Itsunori Onodera, chairman of the study group, said that if a missile “will fly from North Korea in tens of minutes, Japan should also consider its strike capability to prevent from the second shot.”
In fact, the study group’s recommendations are quite modest. It uses the expression “counter-attack capability” and is not recommending that Japan seek a “preemptive strike capability.” Moreover, it recommends that even if Japan has its own capabilities, they will function within the framework of the U.S.-Japan alliance. Japan’s counter-attack capabilities are intended to limit damage from a second and third wave of attack from North Korea rather than be a deterrent. Even if Japan cannot prevent the first salvo attack, it can reduce and suppress the number of remaining North Korea’s missiles before the next wave, and the probability of interception by missile defense improves.
Therefore, to contribute to deterrence by denial and to limit damage if deterrence fails, Japan must strengthen its missile defense capabilities. According to the FY2017 defense budget, the Ministry of Defense plans to move forward with many new programs. It will accelerate investment in BMD systems, upgrade an Aegis destroyer, procure SM-3 Block2A, and PAC-3 MSE. In addition, Defense Minister Tomomi Inada has suggested considering the introduction of new BMD systems such as the Aegis Ashore. If Japan introduced additional BMD systems, the Japan Self-Defense Force (JSDF) could better protect not only its own assets and citizens, but also the assets, personnel, and dependents of U.S. Forces Japan.
The flexibility of Aegis Ashore would be a very tempting. This system would significantly improve Japan’s integrated air and missile defense (IAMD) architecture. A Mk41 multiple vertical launch system could use not only SM-3s to protect against ballistic missiles, but other interceptors such as SM-6s to protect against aircraft and cruise missiles. Through the development and acquisition process, the United States and Japan will have several opportunities for collaboration, such as licensed production of the Mk41 as well as a joint development project for a new advanced radar system. Moreover, Mk41 could also launch Tomahawk cruise missiles. The U.S. ground-launched intermediate range missile capability has been limited by the Intermediate-Range Nuclear Forces (INF) treaty. However, its potential deployment by the JSDF may provide an option for Japan.
Some Republican senators, such as Tom Cotton and Ron Johnson, have submitted a bill to consider additional deployment of Aegis Ashore in Europe and Asia as a counter to Russia’s violation of INF treaty. This suggests that Aegis Ashore can respond to diverse threats, and it is necessary to make efficient procurement adjustments in the United States and Japan. In addition, it is also important that the Tomahawk and SM-6 are being modified to provide for long-range ship attack capabilities.
If the Japanese government decides to acquire the Aegis Ashore, it may be difficult to procure THAAD as well because of budgetary circumstances. However, from the perspective of strengthening layered BMD, deploying the U.S. THAAD battery to Japan will definitely be an effective measure for ballistic missile salvo attacks. Aegis Ashore can increase the opportunities to intercept at mid-course along with original “offshore” Aegis BMD already owned by JSDF, but it cannot fill the gap between mid-course and terminal phase carried by PAC-3. THAAD can provide not only the upper terminal defense capability, but also the ability to strengthen the point defense capability against the hypersonic boost-glide vehicles that are difficult to mid-course interception.
In addition, the PAC-3 MSE can be integrated with THAAD’s radar systems (AN/TPY-2) and, with upgraded software, would extend PAC-3 MSE’s intercept range. Japan’s BMD system should be further integrated with the U.S. deployment system creating a U.S.-Japan ground based interceptor joint task force. Furthermore, in the coming years, THAAD is expected to be upgraded to develop a three-fold increase in range, a nine- to twelve-fold increase in the defended area, and a hypersonic glide interception capability.
The General Security of Military Information Agreement (GSOMIA) agreement between Japan and South Korea is promising and opens the door to greater trust and cooperation among allies. Since 2016, the Japanese, U.S., and ROK navies have conducted four trilateral missile warnings and information sharing exercises. If North Korea’s provocations continue, the three should conduct a practical field training exercise, including a live missile intercept. More rapid, integrated, and seamless response requires an effective allied sensor system including U.S. Forces Korea (USFK)’s TPY-2 radars, Aegis systems, and interceptors through the C2BMC (Command, Control, Battle Management and Communication) in Hawaii.
According to some U.S. officials, USFK’s THAAD and its TPY-2 radars will not be integrated into other regional BMD networks, including the C2BMC. This was reportedly undertaken to reassure China that the TPY-2 radar could not detect its ballistic missile launches as a forward-based sensor. Even if the TPY-2 radar operated in forward-based mode, it would not be able to detect ICBMs launched from the central Chinese missile sites, as they would follow a trajectory far north and west of the Korean Peninsula en route to the United States.
However, this BMD network would strengthen regional resiliency against China’s regional strike capability. Thus, it could be additional leverage if China fails to deal with North Korea’s nuclear and missile development. As the North Korean nuclear and missile threat grows, Japan, the United States, and South Korea must work together to take practical steps to contain and deter North Korean aggression. Improving Japanese defense capabilities would be an important step in the right direction.
Masashi Murano is a research fellow at the Okazaki Institute. He is a member of the working group that deals with crisis simulations and defense force planning at the Japan Institute International Affairs (JIIA).