Japan has proposed developing a submarine-launched hypersonic guided missile capable of exceeding Mach 5, included in the Ministry of Defense budget request published in late August 2026. The initiative is paired with approximately ¥48 billion for research into an underwater vertical launch system designed to accommodate larger long-range missiles aboard Japan Maritime Self-Defense Force submarines, extending sea-based firepower and complicating adversary targeting.
The proposed capabilities are intended to enhance the survivability of Japanese strike forces by utilizing concealed undersea platforms rather than relying exclusively on fixed air bases and land-based launchers exposed to persistent surveillance. The underwater vertical launch cells would allow future submarines to carry larger stand-off weapons without restricting missile dimensions to conventional torpedo tubes, while preserving space for anti-submarine and anti-surface operations, according to Army Recognition.
The defense budget request also includes research into a stand-off missile launch module for unmanned underwater vehicles, adding another element to a distributed strike architecture. While technical and operational challenges remain regarding submarine hull design and acoustic characteristics, the proposed investments indicate a shift toward ensuring long-range strike capabilities can survive the opening phase of a conflict in the East China Sea and Western Pacific.
