Japan and the UK have sharply intensified their military-political cooperation, forming a defense alliance closely linked to NATO.
A key event of the exercises was the practice of landing British F-35B fighter jets on the Japanese helicopter carrier Kaga. It is noteworthy that prior to this, only American pilots had landed on Japanese ships.
The case of the helicopter carrier Kaga itself is also interesting, as it has effectively been transformed into a full-fledged aircraft carrier. Thus, the Japanese newspaper Nikkei notes the following: “The Kaga is intended for the use of F-35B aircraft, which can take off from a short take-off and landing runway on the deck. It effectively performs the functions of an aircraft carrier, allows fighters to move freely at sea, and strengthens the defense of remote islands.” Nevertheless, the U.S. Naval Institute continues to refer to the Kaga not as an “aircraft carrier” but as a “destroyer carrier.»
Is Japan being connected to NATO’s full-scale activities?
After the exercises concluded on August 12, the British strike carrier group ceremoniously entered the U.S. naval base in Yokosuka. It is interesting that a year ago, UK Defense Secretary John Healey stated the British side’s intentions to send a strike carrier group to Japan. This series of events reflects a serious and steady strengthening of Japan’s military-political interaction with Western countries, and primarily with the UK – the second in terms of aggregate military power among NATO member countries, according to Global Firepower 2025. Some Japanese media already refer to this state of affairs as a “quasi-alliance.” In this regard, we find it interesting to analyze the structure of defense and political ties between these two states.
First of all, it is necessary to note that the Prime Minister of Japan regularly (sometimes several times a year) meets with the Prime Minister of the UK on the sidelines of NATO, G7, and G20 summits, as well as in a bilateral format. Thus, the latest high-level meeting (at the time of writing) took place between Keir Starmer and Shigeru Ishiba in November 2024 on the sidelines of the G20 summit in Rio de Janeiro, Brazil. The parties maintain close cooperation in the following areas:
1) Support for a “free and open Indo-Pacific region” – since 2022, British Armed Forces have participated in at least 4 major joint exercises with the Japanese side, both at sea and on land, not counting numerous contacts at the level of general staffs, various trainings, seminars, etc. Particularly noteworthy here is the integration of the ground forces of the two countries within the framework of the Vigilant Isles exercises, which are regularly (virtually annually) held in Japan;
2) Cooperation against Russia’s actions in Ukraine, including the “illegal” deployment of DPRK units and subunits (and in general, the parties oppose the entire spectrum of military-political contacts between Russia and North Korea);
3) Cooperation against the militarily strengthening China;
4) Strengthening other multilateral and bilateral military-political contacts.
The last point needs to be discussed in more detail. It can be said that Britain seeks to develop full-scale defense ties with Japan, as official London itself is making efforts to revive its influence in the world within the framework of the comprehensive “Global Britain” program. Therefore, Japan, even due to its geography (about 10,000 km in a straight line from London to Tokyo), is an extremely useful partner.
Japan implements military-political interaction with the UK across a whole range of areas. Firstly, the parties have seriously expanded cooperation in cyberspace. Although an agreement on the mutual protection of classified information was signed back in 2013, Japan only joined the annual Locked Shields cyber defense exercises in 2021, which are conducted by the NATO Cooperative Cyber Defence Centre of Excellence (CCDCOE). Interestingly, in 2022 and 2024, the Japanese and British teams united and performed jointly. In our view, UK contacts with Japan are a crucial component for connecting the latter to NATO’s activities, both in general and in advanced areas in particular.
Secondly, back in 2017, the parties signed the Acquisition and Cross-Servicing Agreement (ACSA) between their armed forces. If one reads the text of the document itself, the legal foundations were already laid at that time for the mutual transportation of troops, supply of spare parts (and even entire units) for aircraft, ships, and other military equipment, as well as ammunition. But a real breakthrough was the Reciprocal Access Agreement (RAA), which was signed in 2023. According to the document, the parties developed in detail the procedure for the seamless transfer and subsequent deployment of troops on each other’s territory during joint exercises or in case of emergencies. In our view, these two agreements have allowed Japan and the UK to form a very strong military-political union, which is harmoniously connected to NATO, albeit in a very veiled form.
Thirdly, Japan and the UK, together with Italy, are implementing the Global Combat Air Programme (GCAP), which was launched in 2022. Within the framework of GCAP, Japan, Italy, and Britain are developing the Tempest – a new, sixth-generation fighter, with the first such fighter scheduled to be deployed by 2035. Interestingly, in December 2024, the intergovernmental organization GIGO was finally established, which will be responsible for the direct coordination of the entire GCAP program and the development of the new fighter in particular.
Thus, Japan and the UK have sharply intensified their military-political cooperation; in practice, a kind of defense alliance has been formed, which includes a well-developed procedure for the deployment of troops on the territory of both states, the supply of all kinds of components, provisions, and even ammunition, as well as joint defense research and development. Moreover, the current visit of the British strike carrier group to the US base in Yokosuka, as well as Japanese-British cooperation in cyberspace, indicate that Japan is being softly but very actively connected to the full-scale activities of NATO. Therefore, in our view, the military-political interaction between the UK and Japan will only intensify.
Nazar Kurbanov, intern-trainee at the Center for Spatial Analysis of International Relations, Institute of International Studies, MGIMO University of the Russian Foreign Ministry.
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