Policy Briefs on Peace and Security in Northeast Asia

This policy brief aims to assess the likely diplomatic trajectories of Japan in the post-Ishiba era. The outcome of the 4 October LDP leadership election will not only mark a turning point in domestic politics but also significantly impact Japan’s core diplomatic relations with the United States and China. The brief evaluates how the choice of centrist vs. hardline conservative orientations will affect Japan’s relations with China, the United States, and the broader region.

This policy brief analyses the rise of Sanseitō and the implications of its agenda for Japan’s civil-military relations. It argues that the party’s push to elevate moral education, revise the constitution, and centralize the military command directly threatens the civil–military balance. The convergence of generational change, worsening security perceptions, and rising nationalist sentiment has made large segments of the Japanese public, especially youth, more receptive to Sanseitō’s message. This trajectory risks undermining civil–military relations by eroding civilian control and enabling the militarization of education. The brief concludes by outlining policy recommendations to reinforce civilian supremacy over the military, support civil society’s watchdog role, and mitigate political polarization.

To prevent any unintended military conflict and provide reassurance over Taiwan, it is essential for all parties to acknowledge the Taiwan military as a legitimate ‘military entity’ and establish communication frameworks among regional forces. Despite political sensitivities, Taiwan’s military presence is a reality. Treating Taiwan as a military entity is not a matter of sovereignty but of practical security. Any conflict between China and Taiwan would have catastrophic consequences for the international community, with Japan and neighbouring countries directly affected. History has shown that wars often stem from miscommunication and misjudgement; therefore, Japan must lead efforts to promote dialogue and build mutual trust, laying the foundation for lasting reassurance and regional stability.

This policy brief seeks to answer a critical question: What kind of reassurance can Taiwan give to Mainland China, and vice versa? It also points out two important questions with preliminary answers: What could be the reassurance measures given by major stakeholders in the region, and is reassurance possible given the identity politics in Taiwan and Mainland China? The brief first discusses the term ‘reassurance’ with reference to theoretical literature, then analyzes the recent deterioration of cross-strait relations, with no Track I dialogue, very little official communication, and a military standoff. Next, the brief provides a list with examples of possible reassurance measures that could be taken by the two sides of the Taiwan Strait. Before concluding, the brief argues that United States’ influence and the impact of Taiwan’s identity politics need further discussion.

This policy brief examines the rise of the Sanseito and the Japan Conservative Party in the July 2025 Japanese Senate elections, through three key lenses: (1) public discontent with the LDP and the fragmentation of the conservative base, (2) external factors driving nationalist sentiment amid a deteriorating security environment, and (3) internal factors, including economic stagnation and rising anti-foreigner sentiment. By analyzing these dynamics, we aim to illuminate the broader political and social implications of this electoral shift.