By Jun Kajee & David F.J. Campbell
Japan is not abandoning its alliance with the United States. It is accelerating defense spending, deploying longer-range strike capabilities, strengthening the defense of its southwest islands, expanding maritime surveillance, and building a broader network of security partnerships across the Indo-Pacific and Europe.
Under Prime Minister Sanae Takaichi, Tokyo’s shift reflects a harder strategic calculation-that the U.S-Japan alliance will remain the foundation of Japanese security, but American military resources, attention and forward presence can no longer be taken for granted.
China’s military expansion is the most immediate driver of this transformation. Japanese planners face growing Chinese air and naval activity around the East China Sea, the Ryukyu Islands and Taiwan. Japan’s 2022 National Security Strategy identified China as the “greatest strategic challenge” facing the country, while the Takaichi administration has accelerated the planned increase in defense spending, considering a lofty 3.5 percent of GDP target. To be clear, Japan is not withdrawing from the U.S.-led security architecture—but it is taking steps towards making that architecture less dependent on the United States alone.
This diversification has become more consequential under Trump 2.0. Washington continues to regard China and the First Island Chain as central strategic priorities, but the administration has simultaneously demanded greater allied burden-sharing, emphasized a more distributed and survivable force posture, and demonstrated a willingness to redirect substantial military resources toward other theaters. The current conflict with Iran has made this trade-off tangible. U.S. air-defense assets were moved from Korea to the Middle East, while warships and Marine forces operating in the Indo-Pacific were also deployed to the region. These movements did not amount to a total withdrawal, but they demonstrated that U.S. forces available for Indo-Pacific contingencies can be reallocated when Washington’s priorities change.
For Japan, this creates a strategic imperative: if the United States expects allies to carry more of the burden, and if American forces can be redirected rapidly between theaters, Japan must possess more of the capabilities and relationships required to manage regional contingencies itself. Tokyo’s response is therefore not preparation for the abandonment of the U.S.-Japan alliance. It is preparation for an alliance in which Japan must increasingly be capable of acting when American attention, forces or resources are committed elsewhere. CSIS similarly identifies increased Japanese responsibility and defense investment as central to Washington’s evolving alliance expectations.
This is where the concept of Super-Realism becomes salient. The central proposition is that a state can increase its leverage by preserving multiple strategic options and making its future behavior difficult for other actors to anticipate. Trump 2.0 applies this logic to American power: Washington seeks freedom to prioritize the Western Hemisphere, while expecting allies to assume greater responsibility for their own immediate interests. But strategic optionality has a reciprocal effect. When the hegemon becomes less predictable, allies have an incentive to develop strategic options of their own.
Japan is therefore an important test of a broader proposition underpinned by Super-Realism. The same uncertainty that gives Washington greater freedom of action can compel its allies to become more capable, more networked and less dependent on American intervention. Japan’s defense buildup and expanding partnerships may consequently represent more than merely a reaction to China’s rise. It could also be an adaptation to the changing distribution and commitment of American power.
Tokyo’s response operates across three levels. First, Japan is expanding indigenous military capabilities, including stand-off weapons, maritime surveillance, missile defense and defenses around the southwest islands. Its defense spending has risen rapidly, while the government has accelerated capabilities designed to deny access to Japanese territory and surrounding waters. These investments give Tokyo greater capacity to respond independently during the opening stages of a crisis rather than depending entirely on immediate U.S. support.
Second, Japan is strengthening regional security networks. Defense cooperation with Australia, the Philippines, South Korea and other Indo-Pacific partners provides additional channels for intelligence, maritime awareness, logistics and operational cooperation. Japan’s Official Security Assistance programs are particularly important because they extend Japanese security activity beyond the home islands and contribute to a wider regional surveillance architecture.
Third, Japan is diversifying beyond the Indo-Pacific. Tokyo has deepened defense cooperation with the United Kingdom, France and Germany and expanded security cooperation with the European Union in maritime security, cyber, space and other domains. Their significance is that they provide Japan with additional strategic, technological and industrial relationships at a time when uncertainty about American priorities has increased. Japan and the EU held their second Security and Defence Dialogue in May 2026, explicitly expanding cooperation in maritime security, cyber, space and other areas; Japan and Germany likewise agreed to deepen defense cooperation across land, maritime and air domains.
The European dimension is particularly important because it suggests that Japan’s adaptation is not limited to balancing China geographically. If Japan were responding only to the immediate Chinese threat, its most obvious strategy would be to concentrate resources within the East Asian theater. Instead, Tokyo is also cultivating relationships with capable European states that can provide diplomatic, industrial, technological and military alternatives. The pattern is therefore consistent with a broader effort to increase strategic optionality.
Observers are thus faced with a paradox. Super-Realism may increase American leverage in the short term by making allies and adversaries alike prepare for multiple possible U.S. contingencies. Yet the same uncertainty can encourage allies to hedge against Washington itself. The more capable those allies become, the less dependent they may eventually be on American guarantees alone. Tokyo is not dismantling the U.S.-led security architecture; it is helping to redesign it—from a system built primarily around American power and bilateral alliances toward a denser network in which capable regional states assume larger roles.
Japan therefore provides a test not of whether it is itself “Super-Realist,” but of whether Super-Realism produces allied strategic adaptation—and, ultimately, a more decentralized regional security architecture.
Jun Kajee is a Lecturer at Southern Utah University and holds research positions at the Korea Institute for Maritime Strategy, the Indo-Pacific Studies Center, and the SeaLight maritime transparency initiative at Stanford University’s Gordian Knot Center for National Security Innovation. His work has been featured extensively in the media—garnering acclaim from outlets such as Newsweek, The Economic Times, Nationwide News Australia, CommonWealth Magazine and The Institute for the Study of Diplomacy. His research has received funding and support from the United Nations, the European Commission and the United States Bureau of Educational and Cultural Affairs, amongst others.
David F.J. Campbell is an Associate Professor for Comparative Political Science at the University of Vienna. His thematic core focuses are the quality of democracy from a global perspective, knowledge and innovation in a knowledge economy and knowledge democracy, where David co-created (together with Elias G. Carayannis) the concept and theory of the Quadruple and Quintuple Helix Innovation Systems. Additional themes of his include interdisciplinary and transdisciplinary research in the sciences and arts.
