A South Korean court has handed down jail terms to contractors tied to Taiwan’s submarine program, saying they leaked sensitive torpedo-launch system designs in a case judges warned could become a “major diplomatic burden” for Seoul. The ruling, issued by the Masan Branch of the Changwon District Court, underscores how deeply arms cooperation with Taipei can cut across South Korea’s delicate balancing act with Beijing.
Court documents show the chief executive of one South Korean firm was sentenced to two and a half years in prison, and two employees at another contractor received terms of one and a half years each. The companies and defendants were not named, but the ruling did identify their lawyers, who declined to comment on the outcome.
The defendants had been hired to build torpedo-launching tubes and storage systems for Taiwan’s submarine project, but prosecutors argued they crossed a line by sharing highly classified design information without approval from South Korea’s Defense Acquisition Program Administration (DAPA), the country’s national arms-sales regulator. The court agreed that what was exported amounted to “strategic technology,” and said the transfer posed a potential threat to South Korea’s own security given the broader tensions in East Asia.
In its written opinion, the court emphasized that sending such technology to Taiwan — a self-ruled democracy that China claims as its own territory — was particularly fraught. South Korea, like most countries, maintains formal diplomatic ties with Beijing, not Taipei, even as it develops growing security and industrial links with Taiwan. Judges warned that the case risked becoming a “major diplomatic burden” for Seoul if not handled firmly.
The contractors denied wrongdoing, insisting that the materials shared with Taiwan did not qualify as trade secrets or sensitive technologies requiring export licenses. But the court rejected that defense, pointing to the level of detail in the designs and the absence of clearance from DAPA. Taiwan’s defence ministry redirected questions to CSBC, the state-linked shipbuilder leading the island’s indigenous submarine programme, which did not immediately respond to requests for comment.
Taipei is pushing ahead with plans to build eight homegrown submarines, though the effort has faced delays and political headwinds. The prototype vessel only reached its maiden sea trial in June, and the island has had to navigate a thicket of export controls and quiet partnerships to source key components. Taiwan’s government has made military modernisation a central plank of its defense policy, pledging to pour more money into its armed forces as the threat from China grows. Plans to boost defence spending by a fifth next year would push the budget above 3% of GDP as Taipei invests in new systems and signals to the United States that it is serious about burden-sharing.
This is not the first time South Korean contractors on Taiwan submarines have faced legal scrutiny. In 2023, prosecutors citing the risk of Chinese economic retaliation charged a third Korean contractor with violating trade laws tied to the program. That firm ultimately saw its conviction overturned, but the new sentences highlight how efforts to help strengthen Taiwan’s undersea deterrent can carry significant legal and diplomatic risks for partners operating in China’s shadow.
