Hai Kun-class

The Hai Kun class ("Narwhal"), product of Taiwan's Indigenous Defense Submarine (IDS) program, is the first submarine ever built on the island — a strategic milestone after two decades of failed attempts to buy boats abroad in the face of Chinese diplomatic pressure. The design is believed to derive from the Dutch Zwaardvis class, which Taiwan operates as the aging Hai Lung class, extensively modernised with covert technical assistance from several Western countries.

At roughly 70 meters and 2,500 tons surfaced, the boat uses diesel-electric propulsion with lithium-ion battery technology — following the Japanese lead — in place of a conventional AIP system, an X-form rudder and six 533 mm torpedo tubes firing the US-supplied Mk 48 Mod 6AT heavyweight torpedo, with compatibility for the UGM-84L Sub-Harpoon missile.

The lead boat was launched at CSBC's Kaohsiung yard in September 2023, began sea trials in 2025 and was delivered to the Republic of China Navy the same year. Up to eight boats are envisioned to replace the two Hai Lungs and hold the strait against a vastly larger Chinese fleet, making the class the centerpiece of Taiwan's asymmetric defence strategy at sea.