Global Britain Meets Rising Japan: Why This Alliance Just Got Real

As Royal Navy flagship HMS Prince of Wales docked in Tokyo Bay in August, it carried with it more than a flotilla of vessels, aircraft, and sailors.

It was also carrying a message: The United Kingdom is not simply gazing at the Indo-Pacific, but it is heavily investing in Japan, one of its major partnerships.

The visit of Britain’s carrier strike group was historic. The visit was the first time ever that a foreign aircraft carrier has visited Tokyo, and it signals a new beginning for a relationship reaching record highs.

Bolstering Sovereignty

The symbolism was powerful: Four thousand British soldiers, fifth-generation fighter aircraft, and the Royal Navy’s newest warship flowing into Japan’s capital city sent a strong message that European and Indo-Pacific security go hand-in-hand.

British Defence Secretary John Healey said, “The security of the Indo-Pacific is interlinked and indivisible with security in the Euro-Atlantic.” His Japanese counterpart, Gen Nakatani, described bilateral defense relations as “unprecedented.”

During a single port visit, the United Kingdom showed that “Global Britain” is not a slogan but a policy—and that policy looks to the east, intentionally.

The Global Combat Air Programme (GCAP) is the best example of how far this cooperation has reached. Under the GCAP, the UK, Japan, and Italy are working to jointly develop a sixth-generation fighter jet. The timing is always uncertain, but it is planned to join the service by 2035.

The jet must be highly capable, but the project is about sovereignty and trust. Through joint design, technology, and investment, the three countries are committing to a future where they are partners, not dependents. For Japan, GCAP is a diversification away from dependence on U.S. procurement. For Britain, it satisfies a long-term strategic interest in the Indo-Pacific. The formation of a joint industrial venture—Edgewing—and a GCAP International Government Organisation to be located in the UK attests to the depth of the commitment. GCAP is the crown jewel of UK-Japan defense collaboration.

GCAP Fighter. Image Credit: Creative Commons.

GCAP 6th Generation Fighter.

From the Carrier Deck to the Cyber Realm

During the visit, the UK’s F-35Bs took off from Japan’s carrier JS Kaga, demonstrating a kind of trust and technical interoperability that few allies ever achieve. The exercise was enabled by Japan’s first-ever Reciprocal Access Agreement with a European partner, reached in 2023. Under the agreement, joint training, deployments, and exercises are permissible on each other’s soil, and the arrangement provides a valuable framework for sustained presence and operational activity in the Indo-Pacific region.

The partnership is expanding to new areas. Both countries are making significant investments in cyber cooperation, with joint exercises under the Japan-UK Cyber Partnership. Industrial collaboration is growing through a high-level steering group on future capabilities, leading to initiatives in shipbuilding, power systems, and maritime technologies.

Britain’s defense industry is increasingly being seen in Tokyo as a trustworthy partner, at a time when Japan’s acquisitions are diversifying beyond the United States. Joint land exercises such as Vigilant Isles, as well as multilateral operations with Australia, further solidify such cooperation.

Britain’s turn toward Japan is so crucial now because the Indo-Pacific is no longer a remote and far-flung theater. The battle for leadership and rules in the region will shape global order for decades to come. Threats to Euro-Atlantic and Indo-Pacific stability are linked, from coercion in the Taiwan Strait to cyber activities and attacks on undersea cables.

Tokyo, meanwhile, is revolutionizing its defense and security strategy by stealth. Amid its largest build-up in decades, Japan is seeking likeminded partners who share similar values and a determination to resist aggression. Britain has moved with urgency and enthusiasm to fill that niche.

A Foreign Policy With Substance

For years, “Global Britain” was ridiculed as empty rhetoric by its critics. But the UK-Japan partnership demonstrates conscious action: legally binding agreements, industrial partnerships, exercises integrated into each other, and cooperative operations across the board. This is not empire nostalgia or mercantile opportunism.

It is about securing Britain’s international position in a region of the world that will define the 21st century, with a partner that can and will support it.

The path is clear. The Reciprocal Access Agreement is being implemented. GCAP is entering into developmental stages. Shared naval, air, and cyber warfare exercises are expanding. And Britain’s permanent presence in the Indo-Pacific, once a fantasy, is now fact. The Tokyo arrival of HMS Prince of Wales was a turning point.

But the fundamental story is about the infrastructure of cooperation being built beneath the news.

As the world grapples with an era of uncertainty, from great-power competition to technological disruption, Britain has made a choice. It is looking east, deliberately. And in Japan, it has found an ally that will help create the future.

About the Author: Jonathan Berkshire Miller

Jonathan Berkshire Miller is the principal of Pendulum Geopolitical Advisory and a member of the advisory board of the International House of Japan, based in Tokyo.