North Korea successfully tested a submarine-launched ballistic missile (SLBM) on 24 August 2016, according to the Republic of Korea military. 38 North—the website of the U.S.-Korea Institute, which is devoted to analysis of the Democratic People’s Republic of Korea—reports that North Korea’s SLBM program could achieve an initial operational capability as early as the second half of 2018. It remains uncertain how many of North Korea’s Romeo-class submarines can be equipped with ballistic missiles. Pyongyang’s SLBM development nevertheless poses a significant strategic challenge for Japan, the United States, and South Korea. Trilateral cooperation among these three nations is essential to confront this threat.
SLBMs threaten all three countries. Currently Japan copes with the threat by employing Aegis-equipped destroyers (armed with SM-3 missiles) and Patriot (PAC-3) missile-defense systems, while South Korea relies on Terminal High Altitude Area Defense (THAAD). Intelligence on specific launch points is vital to successfully shoot down incoming ballistic missiles with these systems. Even though Japan has capable Aegis ships, it would be difficult to shoot down an SLBM because the launch timing and position would come as a surprise. Therefore, all parties threatened by North Korea’s SLBMs need a precise submarine common operational picture (Sub COP).
Until now, South Korea has focused only on defending against ground-launched ballistic missiles. This effort requires little corporation with Japan. Without better intelligence, however, missile-armed North Korean submarines will be able to launch attacks wherever and whenever they desire. Trilateral cooperation will be necessary to effectively cope with this new threat.
Japan, South Korea, and, United States should cooperate to share and maintain a Sub COP. A single country’s effort to collect target information might be constrained by resource and asset limitations. But trilateral cooperation makes this easier by sharing information. For example, South Korea has surface warships equipped with state-of-the-art U.S. sonars, while Japan has highly capable antisubmarine warfare aircraft (P-1s), and the United States has ocean surveillance ships (T-AGOSs). If these three counties cooperate, their efforts to build, share, and maintain a Sub COP would improve each other’s security from the SLBM threat.
Cooperation brings side benefits, especially to Japan and South Korea. Maintaining a Sub COP will greatly contribute to securing sea lines of communication around the Korean Peninsula. As was observed in the Pacific war, one of the most important mission of submarines is to destroy shipping and disrupt the sea lines. A Sub COP also would help these nations defend against the wider submarine threat.
There are three challenges for trilateral cooperation for a Sub COP. First, the three countries lack ASW interoperability. Even though Japan and South Korea have significant experience conducting joint exercises with the U.S. Navy separately, there have been almost no opportunities to conduct trilateral ASW exercises. There is much room to improve in terms of interoperability and exercising among the three nations.
Second, there is no mechanism to share tactical intelligence between Japan and South Korea. Currently, the Trilateral Information Sharing Arrangement allows Japan, the United States, and South Korea to share only intelligence of North Korea’s nuclear weapons and missile-related activities. However, because Japan and South Korea failed to ratify the General Security of Military Information Agreement in 2012, both parties are prohibited from sharing submarine-related intelligence.
Third, trilateral cooperation for a Sub COP differs from cooperation on operational plans (OPlans) between the United States and South Korea. Korean Peninsula OPlans cover from peacetime to total war. Even though Japan may not know the details, the North Korea SLBM threat and the proposed trilateral cooperation for a Sub COP will require all parties to reevaluate their plans.
Only a few years remain for Japan, the United States, and South Korea to consider how to cope with North Korea’s SLBMs before they become fully operational. A trilateral effort to establish a submarine common operational picture is vital to assuring peace and security in East Asia.
Lieutenant Commander Saito is a Japan Maritime Self-Defense Force (JMSDF) surface warfare officer specializing in antisubmarine warfare and a researcher for JMSDF Command and Staff College. He is a candidate for a master’s of science in foreign service at the School of Foreign Service, Georgetown University. The views expressed in this article are of the author alone and do not necessarily reflect the stance of the JMSDF.