Aegis Destroyers and Ballistic Missile Defense in Japan and South Korea

The Aegis combat system is quickly becoming the hallmark of sophisticated navies. Specifically, it is an advanced command and control, and an integrated weapons system, which features anti-submarine warfare systems, anti-aircraft warfare systems, the Phalanx CIWS to defend against anti-ship missiles, and Mark 41 Vertical Launch system. Simply put, Aegis uses high-powered computers and radar to track and guide weapons to enemy targets. It was developed by RCA, which was sold to various other American electronics corporations before being absorbed by Lockheed Martin which currently produces the systems. The US Navy has employed the Aegis system on its ships since the 1980s; it is also deployed by the navies of Spain, Norway, Japan, and South Korea. Australia and NATO forces intend to employ the system in the next few years to bolster their missile defense capabilities.

South Korea

ROK bought Standard Missile (SM)-2s in 2009 which would ultimately be used on Aegis destroyers. Aegis ships also have SPY-1D radar designed for early warning. In 2012 ROK also purchased Green Pine  land-based radar from Israel. South Korea’s Aegis ship is the Sejong Daewang (“Sejong The Great”) Class destroyer, aka KDX-III (Korean Destroyer III): a guided missile destroyer, jointly produced by Lockheed Martin and Hyundai Heavy Industries. The KDX-III is nearly identical to the American Arleigh Burke Class destroyer, except for its longer hull which makes it the largest surface ship in the world to carry the Aegis system. Though the ROK’s destroyers carry the Aegis radar tracking software they do not currently have interceptors. The ROK announced this past summer that it would upgrade from SM-2s to SM-6s by 2016, and a budget proposal accepted by the Joint Chiefs of Staff shows plans to procure three additional Aegis destroyers by 2020.


Japan’s BMD is comprised of six SM-3 missiles on their four Aegis destroyers, and the PAC-3 Patriot system. Tokyo is increasing the number of SM-3s from six to eight over the next ten years.

Last year PAC-3 was deployed in Okinawa and Tokyo’s Ministry of Defense HQ in a symbolic demonstration of capability, obviously not practical as using the missiles would, for instance, shatter every window in Shinjuku. Similar demonstrations of defense capability were made in 2009 and 2012 during North Korean missile threats.

Such demonstrations are more show than substance. Japan has other concerns aside from North Korean aggression: stagnant economy, territorial disputes with China, the Fukishima fallout, and the abduction of Japanese citizens by North Korea which is seen as far more pressing than the DPRK nuclear/missile threat, and the assurance of US alliance makes BMD even less of a priority—yet, the Japanese have still chosen to keep those four very expensive Aegis-equipped boats.

Regional dynamics

Japan has a high level of cooperation with the US, not least of which involved the US-Japan Defense Pact and the high assurance value of American military exercises in the region. This starkly contrasts to the minimal cooperation in missile defense between South Korea and Japan, and between South Korea and the US. While the Japanese are content with relying on the Americans for missile defense, South Korea is moving toward an increasingly independent missile defense system.

South Korean Offensive Missile Capabilities

The ROK tested its indigenous ballistic missile system, Baekgom (백곰) system in 1978 and in 1979 the ROK and US made a bilateral agreement limiting the range and payload of South Korean ballistic missiles to 180km and 500kg, respectively. The Baekgom system was replaced with the improved Hyunmu (현무) system in 1982, which completed its first test launch in 1985.

In 1998 following North Korea’s Taepodong-1 intermediate-range ballistic missile test launch, ROK developed the surface-to-air missile codenamed “M-SAM”. The KM-SAM system (as it would be later named) emulates the Russian missile S-300, and the technological cooperation between Russia and South Korea worried American policymakers who felt that the US Patriot system was superior and provided better interoperability with the USFK.

The ROK joined the Missile Technology Control Regime in 2001, which limits missile payload to 500kg and range to 300km, possibly superseding the agreement with the Americans and increasing South Korea’s allowed missile range. In 2002 ROK announced the procurement of 110 ATACMS Block 1A missiles from Lockheed Martin which have a range of 300km, deployed in 2004.

Since 2011 ROK has sought to increase missile range up to 1000km, citing the 1800km range of North Korea’s Rodong-1. In October 2012 the US and ROK agreed that South Korea’s missile range could be up to 800km with a 500kg payload; it was also agreed that unmanned ariel vehicle (UAV) payload could be increased from 500kg to 2500kg.

South Korea is clearly looking to divorce itself from the American missile and missile defense systems, pursuing greater independence in the region.