Why Japan Selected Aegis Ashore For Missile Defence

Japan has opted for the Aegis Ashore Missile Defense System, putting it at odds with South Korea, which is using THAAD.

Debalina Ghoshal
05 March 2018
The Japanese Ground Self-Defense Force (US Army photo by Staff Sgt. Ist Class Corey Beal)


Given Asia-Pacific’s susceptibility to a nuclear attack by North Korea, missile-defence systems in the region are top of the agenda. Last November, North Korea tested a new, more powerful ballistic missile capability, which it says can strike major US cities as well as pass over Japan’s “defence shield.” 

Japan’s Prime Minister Shinzo Abe did not waste any time in responding to the North Korean threat. In December 2017, the Japanese government announced that it had selected the Aegis Ashore Missile Defense System. The other option for Japan was to choose the Terminal High Altitude Area Defense System (THAAD). 

Japan has justified its stance to choose Aegis over THAAD on the grounds that at a cost of $618 million to $706 million, it is less expensive than the THAAD system ($901 million). Aegis can also intercept missiles over a wider coverage area, which means Japan would need fewer batteries to intercept incoming missiles. 

Reports suggest Japan will acquire two land-based Aegis Ashore systems, which would enhance its deterrent capability. One of the distinct advantages of the system is that it would relieve Japanese destroyers equipped with sea-based Aegis missiles from constantly patrolling for defensive purposes only. The destroyers would be able to perform other tasks at sea to improve Japan’s capability to defend itself. 

In addition, Aegis Ashore would only add to Japan’s defensive deterrent capability alongside the Aegis combat system with Standard Missile-3 (SM-3) interceptors and ground-based Patriot Advanced Capability-3 missiles. Moreover, according to Japanese defence officials, a THAAD set up comes with 48 missiles and nine mobile launch pads. To defend a country like Japan, six sets would be needed, whereas the Aegis Ashore system can handle multiple threats simultaneously. 



According to Dr. Tony DeSimone, vice president and chief engineer of Lockheed Martin Integrated Warfare Systems and Sensors, the Aegis Combat System is in wide demand worldwide due to its capability to adapt to warfighting needs. Aegis Ashore is a further credible defence system as Lockheed Martin plans to integrate its Long Range Discrimination System’s key components, which will increase its operational performance. 

The SM-3 will provide Japan with greater scope for shooting down incoming ballistic missiles. As with the Aegis Ashore system, there are reports that the United States is selling the SM-3 Block IIA interceptors to Japan. The Aegis at sea deterrent deploys the SM-3 Block IB interceptors. The desire to enhance defence capabilities is also clear from the Japanese Minister of Defence, Itsunori Onodera’s statement that Japan would “ensure that [it] is able to defend [itself] with a drastic improvement in its ballistic missile defence.” 


Aegis Ashore in Romania where it is used to safeguard NATO's European allies and US forces against potential missile threats (Photo by MDA)



A foolproof defence system is critical to Japanese deterrence as under Article 9 of the Japanese Constitution, Japan is forbidden from developing nuclear-capable offensive weapon systems. Even though it is under the extended nuclear deterrence of the United States, the country has, time and again, doubted the US’s commitment to attack Japan’s enemies with nuclear weapons. 

In addition to the nuclear threat posed by North Korea, the threat from China, on the other hand, is real. While the Japan–North Korea nuclear stand-off is now a regular affair, just like the North Korea–South Korea stalemate, Japan also faces territorial disputes with China over the Senkaku Islands in the East China Sea. China already possesses sophisticated nuclear-capable ballistic missiles as well as cruise missiles. 

Japan also faces a territorial dispute with South Korea over the Takeshima-Dokdo Island, and while Japan does not possess any ballistic missiles, South Korea possesses long-range ballistic missiles, despite a 1970's US-South Korean agreement not to develop such a capability. Thus, developing defensive capabilities is the need of the hour for Japan’s deterrence. 

In fact, according to reports, Japan also plans to add a cruise missile intercept function to the Aegis Ashore, which will incorporate SM-6 interceptors for intercepting cruise missiles that are usually difficult to intercept with only a ballistic missile defence capability, due to the low flying and terrain hugging capability of cruise missiles. The Aegis Ashore system is expected to be operational by 2023. 

Japan is striving to enhance its missile defence capabilities and it has not only taken the threat from ballistic missiles seriously, but also the threat from cruise missiles with equal seriousness. As its hands are tied in terms of developing an offensive deterrent capability, “defence by denial” is the only option, at the moment, to exert its influence in the Asia-Pacific.


Debalina Ghoshal is an independent consultant in nuclear, missile and missile defence-related issues. Her articles have appeared in the Washington Quarterly, the Federation of American Scientists, Comparative Strategy, The Diplomat, Canadian Military Journal, and Canadian Naval Review. Previously, she was a Research Associate at the Delhi Policy Group.


This article is taken from the Winter 2017/2018 edition of Defence Procurement International. To obtain a copy of the magazine,  SUBSCRIBE here.