North Korea War: Why Japan, the U.S., and South Korea Need a Trilateral Alliance


Though the probability of war remains low, the United States, Japan, and South Korea have been bolstering their missile defenses in response to provocations from the Democratic People’s Republic of Korea (North Korea). Though each country officially labels these North Korean provocations as bluster, they have each begun working to protect against any sort of hostile action from North Korea. While defense and foreign policy officials from each of the three countries have sought to project a united front against the North Korean threat, the most glaring hole in the American — Japanese — South Korean security arrangement is that there does not exist a trilateral treaty among the three nations.

Given the strong bilateral ties between the RoK and U.S. and between the U.S. and Japan, this comes as a surprise to most observers. Under the current legal framework, the U.S is obligated by treaty to defend South Korea should it come under attack, just as it is obligated to defend Japan should it be attacked. However, neither Japan nor South Korea is obligated to help the other in the case of an attack.

Why is this the case? The answer as to why there exists no trilateral treaty is rooted in the turbulent history between Japan and South Korea. The especially brutal 35-year occupation of Korea by imperial Japanese forces during the early 20th century still resonates strongly with many South Koreans, and has put Japanese attempts at military integration under intense scrutiny. Recently, a landmark intelligence cooperation pact was shelved due to tremendous public outcry from South Korean citizens still wary of the Japanese military, even though Japan has constitutionally renounced the right to make war. Periodic visits from Japanese politicians to the Yasukuni shrine, which houses Japan’s war dead ((including class A war criminals) have only served to inflame relations between Japan and South Korea.

From an American perspective, this intractable problem is a tremendously frustrating obstacle to Pacific security. With America’s recent announcement of a shift, both militarily and diplomatically, to the Pacific, bilateral relations between Japan and South Korea have never been more crucial. Especially given recent tensions with North Korea, maintaining a healthy trilateral relationship is high on the list of American foreign policy objectives.

Helping to smooth relations between Japan and South Korea will take off some of the burden of the American military, which already has tens of thousands of servicemen and women in both countries, along with numerous air and naval bases. Finally, helping to more closely coordinate military and intelligence assets between the two countries will help the United States more fully develop its Pacific missile defense capabilities, which currently rely on a networked system of radars and interceptor missiles. Under current law, South Korean radars and interceptors cannot shoot down a missile heading for Japan, greatly reducing the response time available to Japanese radar operators to shoot down an incoming missile.

Thought the U.S. is bound by treaty to aid the Republic of Korea and Japan should either come under attack, the lack of a trilateral defense alliance severely undermines the security arrangements of all three nations. In the face of a fiercely belligerent North Korea and a China seen as an “adversary,” the need for this sort of Pacific security relationship is at an all time high.