Introduction

Japan’s ruling Liberal Democratic Party’s (LDP’s) leadership elections are normally staid and predictable affairs. But scandals in the LDP and former Prime Minister Fumio Kishida’s radical decision to dissolve powerful party factions disrupted business as usual. In an unusually dramatic election on September 27, Shigeru Ishiba emerged as the new party president — and automatically became prime minister of Japan. Ishiba, a long-standing fixture in the ruling LDP who had run for the position four times before, surprised many observers by defeating eight other contenders including powerful party veterans, popular “young Turks,” and a prominent female lawmaker. He immediately called for a general election on October 27 as an opportunity to secure a mandate for his policies during the often short-lived “honeymoon” for a new prime minister.

For the United States, Ishiba brings a strong commitment to the security relationship, albeit from an approach and perspective that have the potential to disrupt the current progress in modernizing the alliance. He has advocated for a more equal partnership and for revisiting the foundational documents that govern the status of the U.S. troops stationed throughout the archipelago. It is an open question whether that element of his campaign rhetoric will translate into governing policies; indeed, he has already appeared to walk back some of his positions, including calling for an “Asian NATO” ahead of the general election. With the U.S.-Japan alliance at the center of many regional security arrangements, any significant change to the bilateral relationship could alter the stability and order of the broader Indo-Pacific.

A Close Defeat for the Nationalist Wing of the LDP

In the final ballot, Ishiba defeated the LDP’s most prominent female lawmaker Sanae Takaichi in a tight finish, despite his reputation as being unpopular among his fellow lawmakers. Takaichi, a staunch conservative, later declined to become a member of Ishiba’s cabinet, bucking the practice of joining the winner’s administration and thereby revealing a split in the ruling party. Takaichi was a close ally of former Prime Minister Shinzo Abe, the longest-serving leader of postwar Japan and a highly influential figure in the party before his assassination in 2022. As an Abe protégé, she championed his nationalist views on Japan. Takaichi is a member of Nippon Kaigi (Japan Conference), an ultranationalist organization that supports amending the U.S.-drafted 1947 constitution, including the pacifist Article 9 clause and revision of textbooks to promote patriotism in education. To its detractors, Nippon Kaigi espouses a revisionist agenda that denies Japan’s wartime atrocities and smarts at the humiliation of the defeat of Imperial Japan.

Takaichi pledged that as prime minister she would pay an official visit to the controversial Yasukuni Shrine that celebrates Japan’s wartime dead, including several Class A war criminals (Japanese leaders accused of directing a war of aggression) from the World War II era.  In the past, official visits to the shrine — particularly those on August 15, the anniversary of Japan’s surrender in 1945 — have drawn sharp rebukes from South Korea and China. Ishiba has remained silent on whether he would visit the shrine as prime minister but has voiced support for U.S.–Japan–South Korea cooperation, suggesting he would refrain from angering Seoul with a visit to the shrine. Ishiba’s triumph over Takaichi is widely seen as good news for the future of the trilateral relationship.

Ishiba’s Vision: Implications for the U.S.-Japan Alliance

Ishiba is known as a wonky defense scholar and served as Japan’s minister of defense for a short stint in 2007–2008. In the run-up to his election, he proposed ambitious goals for upgrading Japan’s security role in the Indo-Pacific. He called for forming an Asian NATO to deter China, with the U.S.-Japan alliance at its core. To most analysts, the idea is unworkable, given the different circumstances and geography of the European continent and the Indo-Pacific maritime theater. Ishiba further outlined his goal to upgrade the U.S.-Japan security relationship to the level of the U.S.–United Kingdom alliance, arguing that the mutual defense treaty should evolve with the times. Domestically, he supports raising defense spending to 2% of the national GDP and establishing a “basic law on national security” that would streamline and consolidate individual pieces of legislation to allow Japan to respond quickly to a geopolitical crisis. Ishiba needs a decisive win in the upcoming elections to establish the political capital to implement the ambitious defense spending goal.

In many respects, the policies and priorities outlined by Ishiba are good news for the U.S. alliance, building on many of the initiatives that the Kishida and Biden administrations championed. He has been strong in his support of the “latticework” of building a network of like-minded countries in the region, such as Australia and the Philippines; there is no question about Ishiba’s firm commitment to the alliance. But Ishiba’s bold vision for retooling the alliance to become a more equal partnership could open up a Pandora’s Box of challenges to the established framework of the alliance that has evolved incrementally over the decades. The Japanese government has demonstrated a steady commitment to upgrading its military capabilities by making the Self Defense Forces (SDF) more operationally flexible through security legislation — most notably the National Security Strategy (NSS), the National Defense Strategy (NDS), and Defense Buildup Program advanced by the Kishida government in 2022 — and Japanese public opinion has shifted from broadly pacifist to more supportive of defense spending. Yet, the basic premise of the alliance remains: Japan gives U.S. forces exclusive use of 85 facilities throughout the archipelago in exchange for U.S. protection of Japan’s security. Reforming or renegotiating aspects of the alliance that Ishiba has at various times proposed could introduce volatility and new tensions in the relationship, if pursued now that he is in power.

Ishiba has advocated for reforming the Status of Forces Agreement (SOFA) for stationing SDF troops on Guam and for allowing SDF forces to train in the United States. These proposals might sound modest, but the United States has long resisted opening up the SOFA, which governs the status and the rights of the U.S. military in Japan, including on criminal matters. Ishiba’s call to revise the SOFA is shaded by his experience as director-general of the Defense Agency (the predecessor to the Ministry of Defense) when a U.S. military helicopter crashed on the campus of Okinawa International University in 2004. The accident incited an outcry from the local population, already sensitive to the safety issues surrounding U.S. bases. Ishiba has publicly criticized how the U.S. military locked down the area, not allowing Japanese authorities to independently investigate the accident. Revising the SOFA would at a minimum involve lengthy, contentious negotiations at a time when the alliance faces more urgent challenges. If the SOFA were to be renegotiated, sensitive issues such as its jurisdictional guidelines for crimes committed by U.S. service members would be hotly contested. Apart from precipitating a contentious debate at a delicate geopolitical moment, the legal dimension of the alliance could shift fundamentally in ways that— to many U.S. military officials — could derail the underlying framework of the security relationship.

Beyond specific alliance matters, Ishiba has been more open about the need for Japan to defend its own interests and has voiced doubts about the reliability of U.S. security commitments to Japan. He has also questioned whether extended deterrence—also known as the U.S. nuclear umbrella — remains sufficiently robust to defend Japan given advances in North Korean and Chinese military capabilities. These anxieties about the United States are not new and, indeed, somewhat widespread in Tokyo, but Ishiba is blunt and more forceful in articulating the concerns. This style contrasts with the Abe and Kishida approach to U.S.-Japan relations, which sought to upgrade the alliance and acquiesced to publicly stating strategic positions that aligned with U.S. priorities in the region.

Close and Far-term Challenges for Ishiba

The coming weeks will reveal volumes about how Ishiba will fare as a leader. Modern Japanese leaders have at times demonstrated remarkable longevity (e.g., Koizumi, Abe) or surprisingly short tenures (Fukuda, Suga).  Parliamentary elections on October 27 will indicate Ishiba’s political strength and whether his mandate is sufficient to carry through the LDP’s ambitious fiscal and defense agendas. Only days later, the U.S. presidential election will determine the next U.S. leader, after which Japan may face a second Trump administration that is likely to take a skeptical view of U.S. alliances. Some of Ishiba’s proposals could introduce tension no matter who wins the U.S. election. In any case, Ishiba—or his successor if his term proves short-lived—will need to sell to the Japanese public the value of investing heavily in Japan’s defense amid other priorities.

Assuming that Ishiba can implement his predecessor’s ambitious defense budget target of 2% of GDP, the question is whether Japan’s investments in defense will continue to be within the framework of close and complementary U.S.-Japan security cooperation or whether it veers in the direction of Japanese autonomy. Ishiba has the background and ambition to play a major role in shaping these foundational decisions on how Japan confronts its security challenges—if he is able to master the LDP’s complicated factional politics and also muster strong public support for his defense goals.