SŌRYŪ-CLASS

The Sōryū-class is the largest non-nuclear submarine ever operated by Japan and among the most capable diesel-electric submarines in the world. Its air-independent propulsion (AIP) system — Stirling engines on earlier boats, lithium-ion batteries on the final two — allows submerged operation for weeks without surfacing, approaching nuclear submarine endurance at a fraction of the cost. Japan's submarine force is specifically optimized for the shallow waters around the Japanese home islands and the East China Sea, where Chinese submarine activity has increased dramatically. The class achieves exceptional quietness through advanced sound isolation mounting of all machinery. Australia selected a modified Sōryū design for its Future Submarine Program in 2016 (before switching to nuclear submarines under AUKUS in 2021). The Sōryū class is being replaced by the Taigei class from 2022.