TOKYO. Shinjiro Koizumi, a leading candidate in Japan’s upcoming leadership election and former environment minister, has described the nation’s ongoing defence expansion as essential to averting armed conflict in East Asia. Speaking at the Foreign Correspondents’ Club of Japan on Monday, Koizumi framed the most significant military transformation since the Second World War as a deterrent measure rather than a provocation.
“Our defence build-up is critical to prevent war, not to wage it,” Koizumi said. “To protect our sovereignty and the rules-based order, Japan must have credible capabilities.” The remarks align with the administration of Prime Minister Fumio Kishida, who last year announced a doubling of defence spending to 2% of GDP by 2027, echoing Nato benchmarks. Tokyo has moved to acquire long-range cruise missiles, advanced fighter jets, and integrated air defence systems.
Koizumi’s intervention comes at a moment of heightened regional tension. China’s military assertiveness in the South China Sea, repeated incursions into Japanese territorial waters, and North Korea’s accelerating missile programme have all contributed to a sense of vulnerability in Tokyo. The ruling Liberal Democratic Party leadership contest, scheduled for 27 September, will offer a referendum on the direction of Japanese security policy. Koizumi is currently polling strongly against other contenders.
On the same day, the United Kingdom offered unequivocal support to the Japanese position. British Foreign Secretary David Lammy, on a visit to Tokyo, signed a joint statement with his Japanese counterpart Yoko Kamikawa reaffirming the “indissoluble commitment” of both nations to regional stability. The agreement includes expanded intelligence sharing, joint military exercises, and co-operation on emerging technologies such as cyber and space defence.
“Japan’s defence build-up is a responsible act by a sovereign nation,” Lammy told reporters. “The UK stands squarely with Tokyo as it takes necessary steps to secure peace in the Indo-Pacific.” The statement underlined the deepening ties between London and Tokyo, buttressed by the Global Combat Air Programme and a reciprocal access agreement signed last year.
Analysts suggest that the UK’s vocal backing is intended to counter Chinese criticism that Japan’s remilitarisation risks an arms race. Beijing has repeatedly denounced the expansion as destabilising. Japanese officials, however, argue that their posture is purely defensive and proportionate to the threat environment.
Koizumi did not directly address the leadership campaign but stressed the need for continuity in foreign policy. “Whoever leads Japan must maintain this trajectory,” he said. “There can be no backtracking on our security commitments.” The comment was widely interpreted as a signal that he, if elected, would sustain Kishida’s defence agenda.
The combined signals from Tokyo and London reflect a wider recalibration of Western strategy in the Pacific. With the United States engaged in strategic competition with China, allies are expected to assume greater responsibility for their own defence. Japan’s build-up is a central plank of this realignment.
Relations between Japan and its neighbours remain delicate. South Korea, under President Yoon Suk-yeol, has moved to repair ties with Tokyo, but domestic opposition to militarisation persists in both countries. Koizumi acknowledged these sensitivities but maintained that deterrence was the only credible path.
“We have learned from history that weakness invites aggression,” he said. “A peaceful Japan is a strong Japan.” The phrase was met with murmurs of approval from the audience of diplomats and foreign correspondents.
The UK’s endorsement adds diplomatic weight to Japan’s ambitions. As the Indo-Pacific becomes the central theatre of geopolitical competition, the London-Tokyo axis is set to play an increasingly prominent role in shaping the region’s security architecture.
