This article explains historical transition of the U.S.-Japan Alliance by applying theoretical frameworks which combine the distribution of power in the world and the degree of threat. The explanation reveals the evolution of Japan’s alliance policy as a minor ally. It suggests that the minor ally’s adaptable behavior in order to respond to the threat and unite with the major ally contributes to the maintenance of the asymmetric alliance. This argument provides an implication to answer why the U.S.-Japan alliance has been maintained although it had unfair or unequal relationship for each ally.

Theoretical frameworks to examine the asymmetric alliance rearrange four basic forms of the minor ally’s alliance policy. They are reflex balancing, buck-passing, hedging, and complementary cooperation. Reflex balancing is to counter a threat and to rely on a major ally. Buck-passing is to make a major ally accept the burden of an alliance. Hedging is to approach a target country while cooperation with a major ally is maintained. Complementary cooperation is to counter a threat and to assist a major ally.

I argue that the combination of the distribution of power and the degree of threat affects the minor ally’s alliance policy as the member of the asymmetric alliance. Their causal relationships have following four patterns. First, if the distribution of power is decentralized and the degree of threat is high, a minor ally chooses reflex balancing. Second, if the distribution of power is decentralized and the degree of threat is low, a minor ally chooses buck-passing. Third, if the distribution of power is concentrated and the degree of threat is low, a minor ally chooses hedging. Fourth, if the distribution of power is concentrated and the degree of threat is high, a minor ally chooses complementary cooperation.

Applying theoretical frameworks of balance of power and threat, I explain four basic forms of Japan’s alliance policy which were adopted by succesive administrations except for three short-lived ones. When war and confrontation were observed in the Cold War period, Japan relied on the U.S. and balanced against the Communist camp’s threat. When leaders’ talks and tension reduction were observed in the Cold War period, Japan depended on the U.S. When the sole superpower U.S. pursued unilateralism and exhausted in the Post-Cold War period, Japan cooperated with the U.S. as the ally while it approached China and Russia. When Senkaku islands problem fell into a territorial dispute in the Post-Cold War period, Japan decided to start collective self-defense with the U.S. Therefore, the implication of this article suggests that the adaptable nature of Japan’s alliance policy to the changes of international environment sustained the U.S.-Japan alliance.

As a part of the Japan-U.S. Alliance, the Japan-U.S. Security Consultative Committee (SCC) is situated at the top of the hierarchical channel for security talks. The SCC played a major role in the management of the Japan-U.S. Alliance during the post-Cold War era as it was reorganized into a “2+2” meeting structure in which two foreign ministers and two defense ministers participate. However, there have been no studies that have tracked the historical changes in the talks system or the talks process.

This paper aims to track the historical transformations in the processes relating to how agreements are reached and to clarify the qualitative changes in these processes until the enactment of the “2+2” system. We will chronologically follow the historical transformations in the Japan-U.S. talks by focusing on the following two points: centered on the “2+2” meetings, how the consulted channels such as the Security Sub-Committee (SSC), the Mini-SSC, and the Sub-Committee on Defense Cooperation (SDC) were utilized in the process of strengthening the alliance; and how actors such as the politicians and the bureaucratic organizations in Japan and the United States spearheaded the agreement. The following became clear as a result of doing this.

In the 1990s, the “2+2” meetings became increasingly important as a type of ceremony that demonstrated the strengthening of an alliance. They also transitioned to being a forum in which each of the channels of consultation was converted into a group of processes. The “2+2” meetings then came to play the role of controlling the deadlines for the targets to be met in each of the consultation channels and the channels themselves. In addition, the meetings were positioned as a part of a “comprehensive mechanism” through which Japan and the United States formulated operational plans during emergencies and critical situations in the areas surrounding Japan.

In the 2000s, there was a change on the Japanese side, whereby the agreement process changed from being led by the Ministry of Foreign Affairs to being led by the Prime Minister’s Office. This strengthened the initiative of the cabinet ministers and expanded the role of the Ministry of Defense, in particular the uniformed members of the armed forces. As a result, the negotiations with the United States were held in the form of a joint team for foreign affairs and defense under the Prime Minister’s Office, allowing them to deal with the political issues that were difficult to coordinate. In addition, the uniformed personnel group within the Self-Defense Force (SDF) made use of it expertise to realign the bases as well as the units of the SDF and U.S. forces in Japan, thereby strengthening the military cooperation.

In the 2010’s, the Japanese side proposed a revision of the 1997 Guidelines for Japan-U.S. Defense Cooperation along with the consideration and coordination of the expansion of the Japan-U.S. roles, including the partial acceptance of the right to have a collective self-defense.

It became clear that the qualitative changes in the “2+2” system as described above had gradually strengthened the framework of the Japan-U.S. Alliance. While “2+2” did not fully function right from the beginning, nevertheless, through the changes in the situation in East Asia post the end of Cold War and other factors, the two countries accumulated an experience of more than 20 years and qualitatively shifted towards more politically, militarily, and pragmatically important engagements.