In late January, Taiwan’s first indigenous submarine, the Hai Kun (海鯤, or Narwhal), completed its first submerged dive, reaching a depth of roughly 50m during trials in the waters off Kaohsiung. By March, it had managed a fifth dive, still well short of the deep-water and endurance tests required before the navy could accept the vessel.
The original delivery deadline of November last year passed months ago. CSBC Corp, Taiwan, the lead contractor, now targets June and the Ministry of National Defense is levying daily penalties for every day the submarine remains unfinished. The Hai Kun was supposed to be operational by now. It is not close. The delays are not new, but together they present a problem that Taipei’s defense planners can no longer ignore.
The Indigenous Defense Submarine (IDS) program, conceived as a bold step toward military self-reliance, has become a cautionary case in the limits of ambition without an adequate industrial foundation.
Taiwan should wind down this program and redirect the billions it would consume toward the asymmetric systems that its defense strategy demands.
Taiwan had never built a submarine before the IDS program began. That inexperience has exacted a steep cost. The Hai Kun prototype alone has cost NT$51.1 billion (US$1.62 billion), roughly three times what Japan pays per boat for its latest Taigei-class diesel submarines and well above the roughly US$900 million South Korea spends on its Dosan Ahn Chang-ho-class vessels.
The full eight-boat IDS program is projected at NT$405 billion over 25 years against an annual defense budget of approximately US$20 billion.
The technical setbacks have been persistent. The Hai Kun missed its April 2024 harbor trial deadline due to delayed delivery of key components and equipment malfunctions.
When sea trials began in June last year, the hydraulic system on the X-rudder failed during the second outing, forcing the crew to steer manually while tugboats escorted the boat back to port.
A third trial uncovered suspected leaks in the main engine’s cooling system, sending the vessel into dry dock for weeks. By late 2024, the prototype had failed more than 10 categories of harbor acceptance tests, prompting the legislature to freeze funding until basic operational readiness could be demonstrated.
Internal management problems have compounded the engineering difficulties. CSBC experienced leadership turnover amid disputes among subcontractors.
Foreign consultants departed, alleging serious systems-integration failures. The presidential-appointed convener stepped down during sea trials.
Chinese diplomatic pressure has blocked direct component sales from many suppliers, and CSBC chairman Chen Jeng-horng (陳政宏) has acknowledged that Chinese People’s Liberation Army (PLA) military attaches visit foreign vendors to discourage sales to Taiwan, resulting in a submarine assembled from components sourced across seven countries, including sonar from Northrop Grumman, combat management from Lockheed Martin and subsystems from Australia, Canada, India, South Korea, Spain and the UK.
One official described the result as “a United Nations of systems.” The integration challenges were predictable and have materialized at every stage of testing.
Even setting aside cost and schedule problems, the strategic case for a small fleet of Hai Kun-class submarines is difficult to sustain. Taiwan plans to build eight boats.
Maintenance cycles and training rotations mean the navy would keep two or three deployed at any given time, a conclusion consistent with the widely used naval rule of thirds.
The PLA Navy, by contrast, operates approximately 60 submarines and has invested in the anti-submarine warfare capabilities needed to find and engage them.
Taiwan’s hydrography further limits the submarine program’s value. The Taiwan Strait is shallow, narrow and dense with Chinese surveillance assets, making it a poor operating environment for diesel-electric boats that must surface or snorkel at regular intervals (the Hai Kun lacks air-independent propulsion). Off the east coast of Taiwan, the more promising approach for submarine operations, the PLA has already adapted.
Throughout 2024 and into last year, PLA Navy warships conducted frequent anti-submarine warfare helicopter drills, rehearsing submarine-hunting operations in corridors where Taiwan might shelter its fleet during conflict.
Port survivability compounds the problem. Any Chinese first strike would prioritize submarine bases with precision missiles — Ukraine’s 2023 Storm Shadow strikes on the Russian Rostov-na-Donu Kilo-class submarine in Sevastopol showed how vulnerable boats in dry dock can be.
Taiwan’s submarines would be based at one or two ports, all within range of thousands of PLA ballistic and cruise missiles. The boats that do not get to sea in time would likely never deploy at all.
The more consequential problem is what Taiwan forgoes by continuing the IDS program. For the cost of the Hai Kun prototype alone, the navy could have built the 60 small missile boats it canceled in 2021, an entire flotilla of mobile, survivable coastal defense platforms.
The contrast with Taiwan’s more promising investments is instructive. Taipei’s Special Budget for Strengthening Defense Resilience and Asymmetric Warfare Capabilities is funding 400 Harpoon Block II coastal-defense missiles (with deliveries running through 2028), a rapidly expanding drone production program, more than 1,000 loitering munitions, HIMARS launchers and 10 minelaying ships. By the end of this year, Taiwan is expected to field the highest density of anti-ship missiles of any comparable territory. These platforms are mobile, dispersible and survivable under fire, the attributes around which Taiwan’s Overall Defense Concept was designed.
A single Hai Kun carries 18 torpedoes and missiles. For equivalent expenditure, Taiwan could field hundreds of truck-launched anti-ship missiles distributed across tunnels, forests and hardened shelters. Mines laid across likely landing corridors would create passive denial zones at minimal cost.
Uncrewed aerial and undersea vehicles could provide surveillance and deliver precision strikes at a fraction of the cost of a crewed submarine.
Losing one platform out of hundreds is a manageable setback. Losing one submarine out of eight is a strategic disaster.
The US has been urging Taiwan in this direction for years, pushing it toward systems described as “mobile, survivable and cost-effective.” Taiwan’s Overall Defense Concept, developed by admiral Lee Hsi-ming (李喜明) under president Tsai Ing-wen (蔡英文), is built on the same logic. The IDS program has always been the exception.
Winding it down would be difficult due to institutional, contractual and national pride factors.
However, Taiwan faces a threat timeline measured in years, while asymmetric systems can be fielded in months.
The IDS program will not deliver a combat-ready fleet until the late 2030s at best. Taiwan’s leaders should retain the Hai Kun prototype for training and research, cancel the remaining seven boats and redirect resources to asymmetric capabilities.
Its security depends on making a Chinese amphibious assault costly and uncertain. A small number of expensive submarines in vulnerable ports does not achieve that.
Hundreds of mobile, distributed systems do. The sooner Taiwan makes that shift in full, the stronger its deterrent posture will be.
Ethan Connell is an assistant director at Taiwan Security Monitor and a graduate student at George Mason University’s Schar School of Policy and Government. His research focuses on maritime security and cross-strait military affairs. Jonathan Walberg is the associate director of Taiwan Security Monitor. He is a doctoral student at the University of Virginia and a fellow at the Center for Security Policy Studies.
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