Tue, Sep 02, 2025 page8

• Japan’s stake in Taiwan’s defense

  • By Christina Lin
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  On Monday last week, American Institute in Taiwan (AIT) Director Raymond Greene met with Chinese Nationalist Party (KMT) lawmakers to discuss Taiwan-US defense cooperation, on the heels of a separate meeting the previous week with Minister of National Defense Minister Wellington Koo (顧立雄). Departing from the usual convention of not advertising interactions with senior national security officials, the AIT posted photos of both meetings on Facebook, seemingly putting the ruling and opposition parties on public notice to obtain bipartisan support for Taiwan’s defense budget and other initiatives.

  Over the past year, increasing Taiwan’s defense budget has been a sore spot in US-Taiwan relations, as well as between the Democratic Progressive Party (DPP) and the KMT, given that any DPP budget proposal needs the approval of the legislature, where the DPP lacks a majority. This in turn has provoked ire from Washington, saying that Taiwan’s neglect to take requisite steps to fortify its defense would undermine US support, as well as render regional allies such as Japan “less motivated to do more for Taiwan’s security.”

  The administration of US President Donald Trump is asking allies to undertake more burden sharing and increase defense spending. NATO has already done so, and key Asian allies, including Taiwan, are expected to do the same. Washington is also building a coalition to support a potential Taiwan contingency, asking Japan, South Korea and Australia how they can contribute, while monitoring Taiwan’s contribution to its own defense.

  However, in the face of domestic political gridlock, it is unclear whether Taipei’s final defense budget would satisfy the US’ and allies’ expectations. This in turn begs the question — if Washington and regional allies lose confidence in Taiwan’s commitment to burden sharing, would they abstain from assistance in a Taiwan contingency?

  One unlikely country would be compelled to intervene — Japan.

  Western analysts often debate whether Japan would intervene in a Taiwan military contingency. Some doubt Japan would play a role, pointing to its constitutional constraints and pacifist-leaning population.

  However, Chinese strategists include Japan in their planning for a Taiwan contingency. They regard Taiwan as geostrategically significant and assess that its successful occupation would allow China to control the sea lanes key to sustaining Japan’s economic lifeline.

  Xiu Chunping (修春萍), a Taiwan academic at the Chinese Academy of Social Sciences in Beijing, has written that Japanese pundits increasingly discuss “Taiwan is Japan’s lifeline.”

  Meanwhile, Ian Easton, associate professor at the US Naval War College’s China Maritime Studies Institute, surveyed open-source Chinese military textbooks, which document Japan’s vulnerability should its imports through the Taiwan Strait be cut off.

  Easton’s report highlighted Chinese military strategists’ own tallies, which document Japan’s reliance on the Taiwan Strait: 90 percent of its oil imports, 99 percent of its mineral resources, all of its nuclear fuel and 80 percent of its container traffic pass through the waterway.

  A 2013 Chinese officer training manual, Japanese Air Self-Defense Force, bluntly states: “As soon as Taiwan is reunified with mainland China, Japan’s maritime lines of communication will fall completely within striking ranges of China’s fighters and bombers... Japan’s economic activity and warmaking potential will be basically destroyed ... blockade can cause sea shipments to decrease and can even create a famine within the Japanese islands.”

  Likewise, Lu Pizhao (陸丕昭), an academic at the Chinese People’s Liberation Army’s Nanjing Army Command College, has described Taiwan as the “Gibraltar of the East” — a strategic chokepoint whose control would give China dominance over Japan’s vital sea lanes, just as the Rock of Gibraltar commands the Mediterranean — and if China seized Taiwan, “all exit and entry routes [into Japan] would be completely suffocated by China.”

  As such, Taiwan’s security is critical to Japan’s security, and its current ambiguous legal status in effect renders it a de facto buffer state between China and Japan — neither under China’s control through annexation, nor under Japan’s control as in its former colonial period.

  If Taiwan were annexed by China, Japan could regard it as an existential threat, similar to its calculus to strike Pearl Harbor when the US cut off its energy supply in 1941. Faced with such a scenario, Tokyo might intervene militarily before the annexation becomes a fait accompli, or even consider acquiring nuclear weapons, as signaled in current debates.

  Japan’s concern over Taiwan’s security is evident in its growing alignment with NATO and efforts to internationalize the cross-strait issue, including calls for an “Asian NATO.”

  In June, Taipei hosted a war game involving numerous retired generals and admirals from Taiwan, the US and Japan — highlighting Japan’s increasing attention to a potential Taiwan contingency.

  However, by the same token, if Taiwan were to lean too far into Japan’s orbit, it could become uncomfortably close for China.

  A more optimal course, therefore, might be to preserve the status quo — with Taiwan’s parties reaching a bipartisan compromise on the defense budget, thereby ensuring continued US and allied backing within a lattice framework for regional security. The ball is now in Taiwan’s court.

  Christina Lin is a senior non-resident associate fellow at the NATO Defense College’s Research Division.
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