The Evolution of the
U.S.-Japan Security Partnership

In the last few years, Japan has taken historic steps to strengthen its defense posture and in turn the U.S.-Japan alliance, which has entered a period of unprecedented integration.

This is a far cry from the time of the alliance’s origins in 1951. With pacifist principles deeply embedded in its postwar constitution, Japan once prioritized economic development and resisted defense cooperation with the United States.

From this starting point, how did Japan evolve into a significant military power capable in its own right of reinforcing deterrence across the Indo-Pacific region?

The CSIS Japan Chair compiled a short history, supplemented by a repository of official statements and interviews with experts, to document the remarkable evolution of this security partnership. This is Alliance Online, a resource tool documenting the evolution of the U.S.-Japan alliance, a security relationship critical to the history—and future—of international relations in the Indo-Pacific and beyond.

Based on the Security Treaty, Japan retained the right to self-defense under Chapter VII, Article 51 of the United Nations Charter. However, Japan also renounced war as a sovereign right under Article IX of its new constitution, written by the United States during the postwar occupation. 

Japan and the United States signed the Treaty of Mutual Cooperation and Security, which allowed U.S. forces to retain bases in Japan after Japan regained sovereignty. However, the first version of the treaty included no obligation for the United States to defend Japan.  

The Strategic Bargain

As Cold War tensions in Asia intensified in the aftermath of the Korean War, the two governments revised the bilateral security treaty in 1960.  

The revised treaty enshrined the U.S. commitment to defend Japan in Article V in return for permission to retain bases in Japan “for the maintenance of international peace and security in the Far East,” captured in Article VI. The United States also retained control of Okinawa until 1972. This was the broad strategic bargain that remains the foundation of the U.S.-Japan alliance to this day. 

In these early days, few in either country thought that Japan would eventually emerge as a true military partner of the United States. 

The massive protests that took place in Japan in response to the revised treaty—which led President Eisenhower to cancel a planned visit to Japan in June 1960—reflected concerns about the potential to become drawn into Cold War conflicts. 

Nevertheless, Japan gradually focused more on defense as the regional security environment became more severe.    

Despite the controversy in Japan surrounding the 1960 security treaty, strategic debates also reflected a parallel concern that a failure to develop defense capabilities could weaken U.S. support for Japan.

This created an “entrapment vs. abandonment” dilemma that animated Japanese defense policy during this period.  

The expansion of Soviet military power in East Asia would eventually necessitate increased emphasis on homeland defense, especially in the surrounding seas, to deter a Soviet attack and secure imports of natural resources critical to Japan’s economy.  

Sea lane defense was the focus of two key documents: Japan’s National Defense Program Outline of 1976 and the Guidelines for Japan-U.S. Defense Cooperation of 1978, highlighting the alliance’s increased importance in the Cold War. This set the stage for Japan’s commitment in 1981 to take on responsibility for defending sea lanes out to 1,000 nautical miles from Japan.

Burgeoning Economic Friction 

Yoshida’s emphasis on economic revival also featured prominently during this period, and by the 1980s Japan’s economic power became a source of friction with the United States. 

The 1985 Plaza Accord was intended to rectify trade imbalances, but it instead increased Japanese investment in the United States and generated criticism of Japan’s economic prowess as the U.S. economy struggled. 

This introduced a new dynamic to alliance ties that threatened to overshadow progress in defense cooperation critical to U.S. strategy in Asia. 

A series of crises in the immediate aftermath of the Cold War precipitated an effort to redefine strategic objectives for the U.S.-Japan alliance.

During the first Gulf War in 1991, Japan considered dispatching the Self-Defense Forces to support peacekeeping operations in response to U.S. pressure but failed to do so and was criticized for “checkbook diplomacy” after contributing $13 billion to support the coalition against Iraq.  

  

Renewal of Alliance Purpose

The collapse of Japan’s “bubble” economy in 1992 and subsequent U.S. emphasis on trade imbalances complicated the bilateral relationship even as the regional security environment deteriorated. Washington became increasingly focused on the threats posed by North Korea’s nuclear weapons program and a newly rising China. But a coalition government in Japan began to emphasize multilateral diplomacy and a focus on Asia over the alliance with the United States. 

Alarmed by the potential for drift in the relationship, then assistant secretary of defense Joseph Nye launched a strategic review of the alliance. He published a report in February 1995 that emphasized the importance of U.S. forward military presence in East Asia in a post–Cold War world.  

In the context of these events, Washington launched a dialogue with Tokyo to define the future of the U.S.-Japan alliance and rebuild the consensus in both capitals about the relationship’s importance. 

This effort culminated in April 1996 with a joint security declaration that affirmed the alliance as the “cornerstone . . . for maintaining a stable and prosperous environment for the Asia-Pacific region.” 

In that document, the two governments agreed to revise the 1978 guidelines for defense cooperation, to include cooperation for the first time in “situations that may emerge in the areas surrounding Japan”—code for a Korean contingency—signaling Japan’s willingness to loosen its traditional emphasis on primarily its own defense to focus more on regional security.  

In 1996, the governments also produced a blueprint for reducing the impact of the U.S. presence on Okinawa, including plans to relocate Marine Corps Air Station Futenma, which is located in a heavily populated area and thus is a symbol of local frustration with the U.S. military presence on the island.  

The terrorist attacks of September 11, 2001, marked the beginning of a new chapter in alliance cooperation. 

In contrast to the Gulf War period, Japan under Prime Minister Koizumi Junichiro moved quickly to support the United States after the attacks and passed special legislation to dispatch Maritime Self-Defense Force vessels to the Indian Ocean in support of Operation Enduring Freedom. 

A similar bill was passed after the onset of the Iraq War to allow the Self-Defense Forces to support reconstruction efforts under Operation Iraqi Freedom. Some 600 Ground Self-Defense Force personnel were deployed to Iraq to provide non-combat support to the war effort.  

Both “special measures” laws were historic and facilitated a role for Japan in international security beyond its immediate region. Initially unpopular, both measures earned public support over time as Japan’s contributions were recognized internationally. 

The expanding role for Japan under Koizumi prompted the U.S. and Japanese governments to initiate a review of alliance roles, missions, and capabilities in a regional and global context. 

The U.S.-Japan Security Consultative Committee or “2+2” process—meetings between the U.S. secretaries of state and defense and their Japanese counterparts—became the driver of progress in the alliance. 

Joint statements in February and October 2005 outlined common strategic objectives for the alliance and added efforts to improve the international security environment as a third pillar for alliance roles and missions (in addition to the defense of Japan and situations surrounding Japan). 

The Great East Japan Earthquake and Rising Threats in Asia 

Frictions over the alliance continued until the Great East Japan Earthquake of March 11, 2011. That natural disaster cast the U.S.-Japan alliance in a new light as the U.S. and Japanese militaries coordinated large-scale humanitarian assistance and disaster relief efforts to support Japan’s recovery. 

By early 2012, the alliance was again on firm footing, and under Prime Minister Noda Yoshihiko the two governments successfully negotiated adjustments to the 2006 force posture plan, preserving plans to reduce the Marine Corps presence on Okinawa while changing the composition of units moving to Guam. 

The need for Japan to strengthen deterrence in response to China’s military ambitions and tensions in the South China Sea and East China Sea subsequently shaped defense policy debates, ultimately yielding new strategies released after the LDP returned to power in late 2012.  

This coincided with a strategic decision on the part of the United States to focus more cohesively on regional affairs under President Obama’s “rebalance to Asia,” reviving a process of strategic alignment with profound implications for U.S.-Japan alliance cooperation. 

Under Prime Minister Abe Shinzo, Japan unveiled its first National Security Strategy in 2013.

This strategy defined Japan’s national interest in strengthening its own defense capabilities, the U.S.-Japan alliance, and partnerships with other like-minded partners in Asia to manage a rising China and shape the regional order. 

The Abe government pushed through a reinterpretation of Article IX of the constitution to allow Japan to exercise the right of collective self-defense under limited circumstances. 

It then prevailed in a contentious policy debate that resulted in a package of defense policy reforms in 2015 to codify the reinterpretations and authorize expanded roles for the Self-Defense Forces in a contingency. 

As a member of the United Nations, Japan already enjoyed the right of collective self-defense under Article 51 of the UN Charter, but since Yoshida, successive governments had chosen not to exercise that right. 

Abe considered this step essential to enhancing Japan’s role as an alliance partner, and though limited in scope, the 2015 reforms allowed Japan to provide direct support for U.S. military operations if an attack against the United States threatened Japan’s survival. 

The range of Japan’s new contributions featured in revised guidelines for U.S.-Japan defense cooperation released that same year. The new guidelines enabled the two militaries to plan for a wider range of contingencies and strengthen interoperability between them.  

Enhancing Defense Cooperation 

The Russian invasion of Ukraine—and Beijing’s support for Moscow—had a galvanizing effect on Japanese public opinion. In 2022, the government led by Prime Minister Kishida Fumio unveiled the second National Security Strategy, a new National Defense Strategy, and a buildup plan to dramatically strengthen Japan’s defense posture and enhance defense cooperation with the United States and other like-minded partners. 

This ambitious agenda includes plans to nearly double the defense budget by 2027, invest for the first time in long-range counterstrike missiles and other capabilities to strengthen deterrence, and bolster Japan’s defense industrial base. 

The April 2024 Kishida-Biden summit in Washington clearly demonstrated a commitment to strengthen defense cooperation with the United States. Kishida also has worked to deepen Japan’s ties with other like-minded partners, including South Korea, Australia, the Philippines, and the North Atlantic Treaty Organization (NATO).  

These changes represent a fundamental departure from Japan’s strategy at the onset of the Cold War, when pacifist principles, concerns about entrapment in military conflict, and a focus on economic power were the dominant features of Japanese strategic culture. 

Japan and the United States are building an alliance that is more integrated bilaterally and with other partners to maintain stability and order in the Indo-Pacific.  

Despite important constraints, including Article IX of its constitution, Japan will likely continue to move away from the Yoshida Doctrine and invest even more in defense to ensure the security of the nation and the region as a whole.  

If the postwar history of the U.S.-Japan alliance is any guide, this process will continue to evolve in response to new challenges that could undermine that order in the future.  

Made possible by support from the
government of Japan. The views expressed are those of the authors.