Taiwan's Domestically Built Submarine Enters Sea Trials to Strengthen Defense Against Chinese Invasion Threat.

According to information published on April 4, 2025, by the "Liberty Time Net", a prominent daily newspaper in Taiwan, Taiwan's first domestically built submarine, the Hai Kun (also known as "Narwhal"), is nearing the completion of its Harbor Acceptance Tests (HAT) and is poised to commence Sea Acceptance Tests (SAT) by mid to late April 2025. This development marks a significant milestone in Taiwan's Indigenous Defense Submarine (IDS) program, aimed at bolstering the nation's maritime defense capabilities in the face of increasing geopolitical tension in the region, especially regarding the growing military pressure from China.
Follow Army Recognition on Google News at this link

Taiwan’s first domestically built submarine, Hai Kun, was transferred from the Taiwan Shipbuilding Corporation (TSMC) dry dock to Pier 91 in February 2025. (Picture source: Facebook page Ship Story)

The HAT (Harbor Acceptance Tests) phase, which assesses the submarine's basic functionalities and systems while docked, has been largely completed. Taiwan Shipbuilding Corporation (TSMC), the contractor in charge of the program, is currently making final adjustments and submitting results to the Navy Command for review. The submarine is scheduled to transition into the more rigorous SAT (Sea Acceptance Tests) phase, which comprehensively evaluates its systems and performance in open water. The SAT is expected to begin this April and conclude by October 2025, with the Hai Kun anticipated to be formally delivered to the Taiwanese Navy in November.

One of the most critical aspects of the SAT phase is the launch of a "control mine" to verify that the submarine's combat systems meet operational requirements. This particular test is slated for late October. After successfully completing all sea trial objectives, the Hai Kun will become Taiwan’s first operational indigenous submarine—a landmark achievement in its defense industry.

In addition to the Hai Kun prototype, Taiwan has laid out a structured plan to expand its submarine fleet through a three-phase production process labeled as "2+3+2", referring to two submarines in the first batch, three in the second, and two in the third. The agreement for the first two production submarines is expected to be signed within 2025. By 2029, Taiwan aims to deploy a fleet of eight domestically-built submarines.

Technically, the Hai Kun-class submarine boasts a submerged displacement of around 2,500 metric tons and can dive to depths of approximately 350 meters—significantly deeper than Taiwan’s existing Chien Lung-class (also known as Stegosaurus-class) submarines. It is equipped with the U.S.-made MK48 Mod 6 Advanced Technology heavyweight torpedoes, widely regarded as one of the most powerful torpedoes in the world, capable of engaging both submarines and large surface warships. Future variants will also feature improved weapon systems, including submarine-launched UGM-84L Harpoon anti-ship missiles, thereby enhancing their strike capability against a range of maritime threats.

The strategic significance of this indigenous submarine fleet cannot be overstated. In the context of a possible military invasion by China—a scenario that has become increasingly plausible amid Beijing's aggressive posture toward Taiwan—submarines offer Taiwan an asymmetric advantage. While China possesses a vastly larger and more modern navy, submarines allow Taiwan to strike strategically, especially against key naval assets, with minimal exposure. These underwater vessels can remain undetected for extended periods, monitor enemy movements, and disrupt amphibious assault operations, making them a cornerstone of Taiwan’s deterrence and defense strategy.

Moreover, submarines enhance Taiwan’s ability to control the waters around its main island and its outer islands, complicating any potential blockade or invasion plan by the People’s Liberation Army Navy (PLAN). Their stealth, endurance, and strike power make them ideal for both defensive and offensive operations in contested waters. The establishment of a domestic submarine production capability also ensures greater autonomy for Taiwan in its long-term defense planning, especially amid increasing difficulties in procuring advanced systems from foreign countries due to Chinese pressure.

The Taiwanese Hai Kun's domestically built submarine's progress toward operational status represents a technological achievement and a strategic turning point for Taiwan's defense policy. The ability to field an indigenous fleet of advanced submarines provides the island nation with a potent tool for national survival and resistance in an increasingly unstable security environment.