Japan’s Rearmament: Technology, Deterrence, and Alliance Dependence

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In 2022, Japan laid the foundations for a new set of defence and security policies that shed the self-imposed post-World War II constraints on its military.

In December 2022, Prime Minister Fumio Kishida’s government revised the three key documents, including the National Security Strategy, after months of debate, unveiling a tougher approach to the region. This shift was shaped by the need to confront the North Korean missile threat, China’s increased muscle flexing, and a sense of vulnerability arising out of Russia’s invasion of Ukraine in February of that year. “Ukraine today may be East Asia tomorrow,” Kishida had said in June. In addition, the first Trump administration’s demands also bred a sense of vulnerability, as Trump publicly criticised the existing US-Japan security pact as being one-sided and demanded that Japan increase its defence spending and financial contribution to the cost of US troops stationed there.

The 2022 defence package, which includes the NSS, the National Defense Strategy, and the Medium-Term Defense Program, articulates a reframing of the Japanese military’s role: from narrowly repelling imminent attacks to deterring aggression through pre-emptive action against a planned hostile assault.

The most far-reaching doctrinal change has been the acceptance of counter-strike, or “strike-back,” capabilities — the ability to attack enemy bases or systems that may be preparing for, or have already carried out, attacks on Japan. The 2022 defence package, which includes the NSS, the National Defense Strategy, and the Medium-Term Defense Program, articulates a reframing of the Japanese military’s role: from narrowly repelling imminent attacks to deterring aggression through pre-emptive action against a planned hostile assault.

Capabilities, Technology, and Military Modernisation

Policy shifts have been accompanied by capability developments. Tokyo has moved to acquire 400-500 Tomahawk long-range cruise missiles and to develop indigenous long-range standoff systems, such as upgraded Type-12 anti-ship missiles. Japan has also decided to expand its missile defence systems, which comprise Aegis ships, land-based interceptors, radars, and space-based, persistent ISR (Intelligence, Surveillance, and Reconnaissance) to detect and defeat saturating ballistic and cruise missile attacks. This includes investments in early-warning satellites.

Some of the most significant investments and effort are also being directed towards unmanned maritime and aerial systems, as well as offensive and defensive cyber capabilities. Enhanced cyberwarfare capabilities will involve adding thousands more cyber specialists to the Self-Defense Forces (SDF) core, raising the total to around 20,000.

Perhaps the biggest boost, however, will be in the area of maritime capabilities. Japan already possesses a formidable navy, though in terms of size it remains no match for its rival, China (see table below).

China versus Japan: Naval Comparison (approx.)

Source: Author’s compilation, with the assistance of Google Gemini.

That said, in terms of technology, Japan is setting a blistering pace. For example, its Taigei-class submarines, equipped with lithium-ion batteries, are among the most formidable conventional submarines in the world. Japan is currently the only country operating such batteries, which provide significantly greater underwater endurance, faster recharging, and silent operations — making Air Independent Propulsion (AIP) systems effectively redundant. Four vessels of this class have been commissioned since 2022, with four more expected by 2029.

There is another area where Japan’s technological thrust is evident: hypersonics. Key to this effort is the Hyper Velocity Guided Projectile (HVGP), which has been in development since 2018 and is slated for deployment next year. With an initial range of 900 km, it is being mooted as a weapon for island defence, though it can also be used against aircraft carriers and ships. The system is launched by a booster from a truck-mounted launcher and then glides to its target. Future variants are expected to have ranges of 2,000-3,000 km.

A complementary project is the co-development with the United States of a Glide Phase Interceptor (GPI) to intercept hypersonic missiles during their mid-flight phase. These interceptors will be fitted onto Japan’s Aegis-equipped destroyers. Together, these systems are expected to come into service in the 2030s, likely ahead of any Western country, including the US.

In September, Japan conducted the first successful test firing of an electromagnetic railgun at a target at sea. Japan is likely to be the first country in the world to deploy such systems. The Japanese intend to use the system to counter hypersonic cruise missiles, as well as a highly penetrative anti-ship weapon.

Japan, whose air force currently depends on around 150 F-35s, hopes to have a sixth-generation fighter enter service by 2035. It is involved in the Global Combat Air Programme (GCAP) with the United Kingdom and Italy to develop the fighter. Another area in which it is seeking foreign technology is unmanned underwater vehicles (UUVs), which have the potential to upend naval warfare in the coming decades. This field stands on the cusp of a revolution that could upend contemporary naval power: individual autonomous UUVs, or swarms, could hunt and track submarines and warships. They could meet the same fate as tanks on land in the face of FPV (first-person view) drones.

Alliance Centrality in Japan’s Defence Posture

Given the sheer size of the Chinese People's Liberation Army (PLA) and its technological edge in areas such as hypersonics, Japan’s catch-up efforts are likely to materialise by the 2030s. Even then, however, it will not be in a position to deal with China by itself. For this reason, its alliance with the US remains an essential element of its defence posture. Yet, through the changes wrought in its defence policy and significant investments in cutting-edge technologies, Japan is signalling to the US that it is not merely a passive, free-loading ally caricatured by Donald Trump.

Given the sheer size of the Chinese People's Liberation Army (PLA) and its technological edge in areas such as hypersonics, Japan’s catch-up efforts are likely to materialise by the 2030s. Even then, however, it will not be in a position to deal with China by itself. For this reason, its alliance with the US remains an essential element of its defence posture.

Not surprisingly, the latest US National Security Strategy recognises this, observing, “Given President Trump’s insistence on increased burden-sharing from Japan and South Korea, we must urge these countries to increase defense spending, with a focus on the capabilities—including new capabilities—necessary to deter adversaries and protect the First Island Chain.” (p.24)

The First Island Chain, comprising the Kuriles, the Japanese islands, Okinawa, Taiwan, and the Philippines, is very much on the minds of Japanese security planners, and this concern is contributing to friction between Beijing and Tokyo.

Japan has already taken steps to sharply boost its defence budget from around 1 percent of GDP to an expected 2 percent in the current fiscal year and has indicated that it is willing to raise it beyond this ceiling as well. With these measures, Japan is expected to emerge as the third-largest defence spender in the coming years, ahead of India.

India-Japan Defence Cooperation

Given its present trajectory, Japan is set to emerge as a major military power once again in the 2030s. In this sense, it will be a useful partner for India, with the two countries located at opposite ends of the Indo-Pacific and united by their shared view of China as their principal adversary.

Although the two countries have a “Special Strategic and Global Partnership,” growing defence ties, and a clutch of agreements and dialogues to promote cooperation, the relationship remains below potential. Efforts to deepen defence technology ties have faltered as much because of India’s indifference as Japanese reluctance.

Although the two countries have a “Special Strategic and Global Partnership,” growing defence ties, and a clutch of agreements and dialogues to promote cooperation, the relationship remains below potential. Efforts to deepen defence technology ties have faltered as much because of India’s indifference as Japanese reluctance. The project to manufacture the ShinMaywa long-range amphibious aircraft stalled, and India’s earlier interest in building the Soryu-class submarine domestically also came to little.

At present, there is an important agreement to transfer and co-develop advanced naval stealth technologies, such as the UNICORN mast for warships and submarines. The two countries also have an agreement to jointly develop an advanced underwater surveillance system and other maritime technologies. However, the potential for expanding joint production of defence equipment by leveraging Japan’s advanced technology with India’s manufacturing capacity has barely been tapped. If pursued with greater political intent and industrial coordination, this cooperation could evolve into a cornerstone of India-Japan defence collaboration in the Indo-Pacific.

Manoj Joshi is a Distinguished Fellow at the Observer Research Foundation.

• International Affairs
• India
• The Pacific
• East Asia
• USA and Canada
• counter-strike capabilities
• defence modernisation
• First Island Chain
• hypersonic weapons
• India-Japan defence cooperation
• Indo-Pacific security
• Japan rearmament
• maritime power balance
• missile defence
• US-Japan alliance

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