Japan’s Intervention in a Taiwan Contingency: It Depends

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Japan’s Intervention in a Taiwan Contingency: It Depends

How a conflict starts, and how the United States responds, would weigh heavily into Tokyo’s considerations.

Japan’s Intervention in a Taiwan Contingency: It Depends

Taiwanese President Tsai Ing-wen, second right, back, Vice President William Lai, right, and Speaker of the Legislature Yu Shyi-kun, third right, wave to Japanese lawmakers during National Day celebrations in front of the Presidential Building in Taipei, Taiwan, Tuesday, Oct. 10, 2023.

Credit: AP Photo/Chiang Ying-ying

In recent years, Japan has faced increased threats from various directions: from Russia to the north, and from North Korea and China to the west. No wonder, as John Mearsheimer once put it, Japan’s defense posture needs to be more like Godzilla and less like Bambi.

This quandary is not new. In fact, for decades, Japan has been on a trajectory of adopting a more muscular defense posture. What is new, however, is Japan’s focus on Taiwan, and the possibility that Tokyo could intervene in a future conflict in the Strait.

The shift toward Taiwan was given fresh impetus in 2021, when Abe Shinzo argued forcefully that a Taiwan emergency would constitute a Japanese emergency, and therefore a contingency for the Japan-U.S. alliance. Last month, Prime Minister Kishida Fumio appointed two new ministers who are more hawkish and inclined towards Taiwan.

But the biggest change in Japan’s defense posture, with significant consequences for Taiwan, is its Defense Buildup Program for FY2023-2027, which will see defense spending increase to 43 trillion yen (nearly $286 billion), a 56 percent increase over the corresponding FY2019-2023 period. Apart from the 9 trillion yen that will be set aside for the repair of defense equipment, the procurement of stand-off defense capabilities is the biggest item in the program, with 5 trillion yen allocated for this purpose. These weapons can be fired at long distances of 1,000-1,500 kilometers, with the mobility and survivability that would enable Japanese forces to reduce the risk of counterattack. They would be instrumental in any Taiwan crisis.

Possible Scenarios

On the surface, Japan certainly looks primed to intervene in a Taiwan crisis, say, if China were to launch an amphibious invasion of the island. If Taiwan put up a fight, this would likely engender U.S. intervention, an intervention that would not be possible without Japan’s assistance. This would involve providing U.S. forces with access to bases in Japan, supporting U.S. forces in rear-end support operations, and even conducting offensive operations further away from Japanese shores.

This in itself is the real-life application of Japan’s overhaul of its security legislation in 2014-15, when the Cabinet decided that Japan’s defense included collective self-defense, that is, going to an ally’s defense when it is attacked.

That said, however, Japan’s response in a Taiwan contingency really depends on the particular scenario, and particularly on whether the U.S. intervenes and what form that intervention takes.

Consider two extreme sets of scenarios. In the first, Taiwan declares independence, prompting a Chinese invasion. Since it was Taiwan that had carried out such a declaration, U.S. intervention – and by extension, Japanese involvement – would be unlikely. The U.S. and Japan have always sought to preserve the status quo across the Strait; a declaration of independence by Taiwan would disturb this delicate balance.

In the second instance, China launches an unprovoked invasion of Taiwan. In this scenario, the U.S. and Japan would be much more likely to intervene. But intervention by the U.S. would have to depend on whether Japan allows American access to U.S. bases in Japan. If Japan did so, it would raise the possibility of China launching attacks on such bases in Japan.

Between these two extremes, Japanese intervention is less likely.

Take, for example, a scenario in which China decides to capture Taiwan’s outlying islands. According to a Japanese scholar I spoke to, this would be akin to Russia’s annexation of Crimea in 2014, where the antagonist grabs a smaller slice of territory before taking a bigger chunk. “This kind of salami slicing would align Taiwan even closer to the United States,” the scholar said. “In this instance, the likelihood of the Chinese operating in Japanese waters and its EEZ is low. Hence, Japanese involvement would be limited.”

A similar outcome might apply in the event of a Chinese blockade of Taiwan. If the U.S. decided to run the blockade, this might engender Japanese forces targeting Chinese assets along the country’s coastline. Again, however, Japanese involvement would be unlikely, given that Tokyo might deem this to be escalatory in the eyes of the Chinese.

The nightmare scenario, as indicated in the widely-reported wargame at the Center of Strategic and International Studies (CSIS) are instances in which Japan takes a more restrained position. Here, Tokyo prevents the U.S. from any military activity on Japanese soil or limits the Japanese Self-Defense Forces to defensive operations. This, CSIS noted, would have a “decisive or fundamental” change in the nature of the battle in favor of the Chinese.

There is no precedent to the U.S. asking Japan for direct or indirect support in contingencies, argues Jeffrey Hornung, a political scientist at RAND. As Hornung observes, none of the critical decisions about Japanese assistance to U.S. operations are “legally automatic.” These decisions are “political, resting with the prime minister at any given moment.”

The Japanese scholar I spoke to talked about another scenario in which Japan and China come to a grand bargain. Under such a deal, China agrees not to attack Japan if the latter fulfills three conditions: it does not attack China; does not support U.S. operations; and does not deploy long-range strike capabilities. The implicit Chinese threat here, the scholar said, would be that Beijing would regard Japan and the U.S. as the same entity if the former provides assistance to Washington.

The third condition is not possible, given that Japan has already embarked on an ambitious program of deploying stand-off missile capabilities and would be very unlikely to decide to stop its deployment. The first and second conditions are plausible, but if Japan decides to decline support to Washington, this would mark the death knell of the alliance.

Political and Operational Considerations

Any Japanese involvement in a Taiwanese contingency would also have to take the country’s domestic politics into account. Some analysts note that Japanese involvement should not be taken for granted and is not popularly supported in Japan beyond the conservative end of the ruling Liberal Democratic Party.

As Jeffrey Kingston at the Temple University in Tokyo notes, there is much admiration in Japan for Taiwan. But there is a “big gap between that sort of warm and fuzzy ‘we like you, admire you’ and all that, and sending troops into harm’s way.” Other analysts note that in one wargame, it took two weeks for the prime minister to declare that there had been an “armed attack on Japan.” This was done out of a desire to avoid a conflict with China. This would tie American hands in its prosecution of any military options.

More importantly, there is no joint operational command between U.S. and Japanese forces. While U.S. Forces Japan is empowered to manage the alliance and keep troops ready, it has no operational role, given that U.S. warfighting commanders are based in Hawai’i. This is quite unlike the South Korea-U.S. alliance, under which both nations are primed to fight on the Korean Peninsula at any time, under the slogan “Fight Tonight.”

Deterrence By Denial

The bigger question is whether Japan would carry out deterrence by denial, which in essence means fostering an environment where any attempts by China to change the status quo by force are unlikely to succeed.

In fact, this is the premise of stand-off weapons, which, as mentioned above, form a big chunk of Japan’s defense spending in the next five years. Given that they can operate from land, sea, or air platforms, the Type 12 SSM (surface-to-ship) missile will have higher wartime survivability. Currently, Type 12 SSMs have a range of 200 kilometers, but upgrades could see their ranges improving to 900 kilometers and eventually to 1,500 kilometers.

The 1,500-kilometer  range, notes Japanese scholar Ken Jimbo, is incidentally the range from Kyushu in the south of Japan to the Taiwan Strait. In essence, these weapons could alter the cost-benefit calculus of Chinese strategists.

“I think Chinese landing craft are the prime target of the ‘standoff capability’ that features in the new NSS and NDS,” said Prof Jimbo, referring to recently released Japanese National Security Strategy and National Defense Strategy documents.

The logic is pretty straightforward: if China contemplates a full-scale invasion of Taiwan, it would have to accept the possibility of counter-attacks by Japanese forces. With a thousand or so missiles deployed in Kyushu and Okinawa, Japan would be in a good position to launch attacks on China’s landing aircraft headed towards the Taiwanese coast.

In essence, this is a primary goal of Japan’s decision to augment its defense capabilities: to deter not only an invasion against the home islands, but also “unilateral changes to the status quo by forces and attempts in the Indo-Pacific region.” This statement in Japan’s NDS document, released in December 2022, is the logical outworking of deterrence by denial. Writ large, this is not only a Japanese undertaking. Other U.S. allies are seeking to change China’s cost-benefit calculus using deterrence by denial.

Australia, for example, is considering long-range strike options, in the event that an adversary establishes a presence in its near region from where it can target Australia or isolate it from its partners and allies. In one case, China could “horizontally escalate’ a conflict with the U.S. to stretch its military resources. In this sense, Marcus Hellyer and Andrew Nicholls argue, that a long-range strike capability is not primarily about a Taiwan or South China Sea contingency.

Given that the Biden administration’s improvements to its regional posture have been modest when compared to its Indo-Pacific rhetoric, U.S. allies such as Australia and Japan are concerned that the U.S. may be unwilling or unable to invest in more forward-deployed military position and deterrence by denial. This is precisely the approach being pursued by Japan and Australia.

In the end, the question over Japan’s involvement in a Taiwan contingency might be less about whether Tokyo intervenes in extremis, but whether, like Australia, it would be able to achieve success in its strategy of deterrence by denial.