Revealed: History's Most Expensive Military Vehicles

8. Soryu Class Submarine – Japan

Builders: Kawasaki Shipbuilding Corporation and Mitsubishi Heavy Industries Primary user: Japan Maritime Self-Defense Force Unit cost: $6.1 million Commissioned in 2009, the Soryu class refines the Oyashio design with an X-shaped stern for agile handling.

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It is Japan’s first boat with air-independent propulsion, marrying Stirling engines and lithium-ion batteries for extended underwater endurance.