The British government has formally endorsed Japan’s largest military expansion since the Second World War, signalling a deepening alignment of Western and Asian security interests against a rising China. The endorsement came as Shinjiro Koizumi, a leading contender to become Japan’s next prime minister, warned that the risk of war in the Pacific was greater now than at any point since 1945.
In a joint statement released after talks between the foreign secretaries in London, the two governments committed to closer defence cooperation, including joint exercises and intelligence sharing. The British endorsement is symbolic as well as practical: it confers legitimacy on Tokyo’s decision to abandon its purely defensive posture and acquire long-range strike missiles capable of hitting targets in China.
Koizumi, who served as environment minister under former prime minister Yoshihide Suga, made his remarks during a visit to the US. He said Japan could not rely solely on American guarantees and must be prepared to defend itself. “The era of strategic patience is over,” he told an audience at the Hudson Institute. “We must face the reality that China’s military buildup and assertive behaviour make conflict a real possibility.”
He described the Taiwan strait as an existential flashpoint, echoing the view of many analysts who believe a Chinese invasion of the island could trigger a wider Pacific war. Japan’s new security strategy, adopted last December, explicitly refers to Taiwan as a matter of concern for Japanese security.
Britain’s endorsement is part of a broader pivot towards the Indo-Pacific. The Royal Navy has deployed the carrier HMS Queen Elizabeth to the region, and the UK has signed defence agreements with Australia and the United States under the AUKUS pact. Japan is in advanced talks to join AUKUS as a non-nuclear partner.
The British statement emphasised shared values of democracy and the rule of law, but the language was notably sharp. It described China’s actions in the East China Sea and South China Sea as “destabilising” and called for “peaceful resolution of disputes without coercion”.
China’s foreign ministry responded by accusing Britain of “meddling in regional affairs” and warned that such endorsements would “encourage militarism and undermine peace”. It repeated its position that the Pacific island disputes are not matters for external powers.
Domestically, Koizumi’s warnings carry weight. He is the son of former prime minister Junichiro Koizumi and is seen as a charismatic leader who could push through constitutional reforms to strengthen the military. His father, who served between 2001 and 2006, was known for his hawkish stance and close alliance with the United States.
The younger Koizumi has positioned himself as a reformer, calling for greater transparency in defence procurement and a more efficient military structure. But his warnings of war risk have drawn criticism from opposition parties and from China, which accused him of “beating the drums of war”.
Analysts note that while a Pacific war remains unlikely, the rhetorical escalation is concerning. The absence of crisis communication channels between China and Japan, and the lack of military-to-military talks, increase the danger of miscalculation.
For London, the endorsement of Japan’s new defence stance is a strategic hedge. As the UK reduces its reliance on the US and seeks new trading partners after Brexit, the Indo-Pacific offers economic opportunities. But it also carries risks. Britain is geographically distant and its military resources are limited. The commitment to Japan may prove hard to sustain if a real crisis erupts.
Nevertheless, the message is clear: the Pacific is no longer a theatre where only the US and China matter. Britain and Japan are now preparing together for the possibility of conflict.
