In its defense budget request for fiscal year 2027, Japan has for the first time separately recorded its intention to develop a long-range missile that can be launched from underwater and that features high survivability. This is reported by RBC-Ukraine, citing The Maritime Executive. The fact that the request is filed as a separate budget line item, rather than as part of a general weapons program, indicates that Tokyo is treating submarine-launched hypersonic weaponry as an independent strategic priority, not as a by-product of fleet modernization.
Two scenarios: ballistic or cruise missile
According to The Maritime Executive, Japan is currently considering two weapon options. The first is a vertical-launch hypersonic ballistic missile. The second is a hypersonic cruise missile powered by a ramjet engine, which could be fired through a submarine's torpedo tubes. Both types share common characteristics: very high speed over long range and the ability to maneuver in flight. It is precisely this combination that shortens the opponent's reaction time and significantly complicates tracking and interception of the missile by air defense and air-and-missile defense systems.
What Japan has today and what is missing
At the same time, Tokyo is still far from the practical implementation of such a system. The Maritime Self-Defense Force currently possesses neither the corresponding hypersonic missiles nor submarines specifically adapted for their use. That said, both directions have already been declared as development programs. In particular, this refers to the Type 25 hyper-velocity gliding projectile project: its Block 2B version is planned to have a range of around 1,620 nautical miles, i.e. about 3,000 km, at speeds of Mach 5 or more. In parallel, work is underway on a less advanced hypersonic cruise missile project with a ramjet engine. The fleet's newest attack submarines remain the Taigei-class vessels, with six 533 mm torpedo tubes capable of launching subsonic Harpoon UGM-84 cruise missiles; as of the current moment, five such boats are in service, the latest — JS Chōgei (SS-517) — having been launched in March 2026.
The nuclear submarine question and the link to AUKUS
Separately, a debate is unfolding in Tokyo over the possibility of building nuclear-powered submarines. Despite constitutional constraints, Japanese Defense Minister Shinjiro Koizumi has openly spoken about the need for the country to acquire such vessels. If Japan truly goes down this path, a future submarine with vertical launch systems could conceptually come close to projects being developed within the AUKUS alliance. This would turn the fleet's submarine component into a carrier not only of cruise but also of ballistic hypersonic missiles.
Threat context: North Korea, China, Russia, and the Ukrainian experience
The strengthening of the submarine component is taking place against the backdrop of growing threats that Tokyo perceives from China, Russia, and North Korea. Submarine hypersonic weaponry holds particular significance for Japan given the development of North Korea's nuclear arsenal: Pyongyang is working on creating a submarine nuclear threat, and Kim Jong Un previously inspected an 8,700-ton displacement submarine under construction. Japan and South Korea are also concerned that Russia may have been helping North Korea develop corresponding technologies in exchange for Moscow's support in the war against Ukraine. Against this backdrop, Tokyo has highly valued Ukrainian drones: the first deliveries of Terra B1 unmanned aerial vehicles from TerraDrone are set to arrive for the Japan Maritime Self-Defense Force in the near future, and drawing on the experience of the war in Ukraine, Japan has developed its own training drone costing around 450 dollars, allowing operators to practice their skills without risking damage to expensive equipment. In addition, Australia and Japan have tested the Boobook laser weapon — the first joint defense-industry project between the two countries.
