Japan’s New Role in Cross-Strait Security

Ships from the U.S. Navy and the Japan Maritime Self-Defense Force underway together after the conclusion of a military exercise.

Tokyo could play a decisive role in deterring or defeating a Chinese attack on Taiwan, but questions remain about its potential involvement.

China’s increasing aggression toward Taiwan has alarmed Japanese policymakers and prompted a rethink in Tokyo about Japan’s approach to cross-Strait security. Though constrained in some regards by its pacifist constitution, Japan is taking steps to prepare for a worst-case scenario conflict across the Taiwan Strait.

To be sure, there is a long history of troubled relations between Japan and China. In more recent times, since the early 2010s China has repeatedly violated Japanese airspace and territorial waters in a bid to exert de facto administration over the Japan-controlled East China Sea islands, known as the Senkakus in Japan, Diaoyu in China, and Diaoyutai in Taiwan.

But the tiny, uninhabited Senkakus are a smaller problem for Japan than China’s intentions to seize Taiwan, and not just because of Taiwan’s paramount position as a semiconductor maker. If Taiwan were to fall, China could easily menace Japan’s most remote southwestern islands, constrict its key trade routes, and further encroach on Japanese administration of the East China Sea islands.

“Japan is a key beneficiary of a rules-based approach to managing the sea lines of communication that link the Indian Ocean, South China Sea, Taiwan Strait, and East China Sea,” notes Stephen Nagy, a politics and international studies professor at International Christian University in Tokyo. He says the Japanese “see conflict or friction across the Taiwan Strait as an existential challenge that would have severe implications for Japan’s economy and national security.

China’s martial muscle-flexing near Taiwan in August marked a turning point for Japan. In a blunt message to Tokyo to refrain from interfering in what the Chinese Communist Party calls “China’s internal matters,” Chinese leader Xi Jinping personally ordered the People’s Liberation Army (PLA) to fire several missiles over Taiwan – shots that landed in Japan’s exclusive economic zone (EEZ).

Japanese Prime Minister Fumio Kishida told reporters in August that the drills were a “serious problem that impacts our national security and the safety of our citizens.”

Since then, Japan has signaled it will focus more heavily on defense. It has announced a plan to double defense spending by 2027, which would make Japan the world’s number-three defense spender after the U.S. and China. Tokyo is also equipping its southwestern islands with anti-ship missiles and air defenses, and is considering buying American Tomahawk long-range (2,500 km) cruise missiles.

The strategically located and highly contested Senkakus have been controlled by Japan since 1895.

An indispensable role

Japan would almost inevitably be drawn into a potential cross-Strait conflict, given its mutual defense treaty with the U.S., Taiwan’s foremost security ally, and proximity to Taiwan – not to mention its strong commercial ties with Taiwan and the cultural and sentimental connections that are a legacy of the 50-year (1895-1945) Japanese colonial presence in Taiwan.

Rick Fisher, a senior fellow at the International Strategy and Assessment Center in Washington, D.C., says that should China ever invade or blockade Taiwan, Japanese involvement would be necessary to defeat the PLA.

“The Sakashima Islands and the Senkakus will have to be armed or turned into bases to support air and missile operations against Chinese forces, while bases like Kadena on Okinawa will be essential to support U.S. air and naval forces that would deploy to the Taiwan area of conflict,” he says.

Japan has the capacity to alter the trajectory of a cross-Strait conflict to China’s detriment in a number of ways, says Eric Chan, a senior strategist at the United States Air Force. For instance, a maximal Japanese response to a Chinese blockade or invasion of Taiwan could include numerous rapid missile strikes on PRC bases and ports.

Due to the geographical proximity of Japan’s Ishigaki to China, Japan is second to Taiwan in terms of capacity to rapidly strike the PRC, he says. Such strikes would increase the logistical difficulty of sustaining a blockade of Taiwan or an outright invasion. Japanese strikes would also significantly complicate PLA air defense operations, particularly if they were done in conjunction with using long-range missiles by Taiwanese, American, and possibly Australian forces.

Even a smaller outside intervention would steeply raise the costs of a PRC blockade or invasion. For instance, if Japan focused on anti-submarine warfare, the PLA Navy (PLAN) “would need to honor this threat either by moving its submarines away from Japan and the Miyako Strait, thus ceding a huge portion of ocean to the Japanese Maritime Self-Defense Force (JMSDF) and the U.S. Navy, or by fighting the JMSDF where it is shielded by land-based anti-ship and coastal defense batteries,” says Chan.

“Either way, a significant portion of the PLAN and PLA Rocket Force would be dedicated to anti-access and area-denial operations versus direct support to the invasion force,” he says.

Grant Newsham, a former U.S. Marine attaché to the U.S. Embassy in Tokyo, agrees Japan could tilt the balance of a cross-Strait conflict. “A capable, competent JSDF (Japan Self-Defense Forces) that’s ready and able to fight, and fight alongside the Yankees, is a huge force multiplier,” he says. “It would cause the PLA no end of trouble – if linked to U.S. forces and operating with them.”

 “Of course, if Japan does decide to fight, it can expect to get hit by the Chinese,” he adds.

Political bottlenecks

Newsham notes that Japan’s political leadership remains cautious about the prospect of intervening in a cross-Strait conflict on Taiwan’s behalf. Those opposed often argue that Article 9 of the Japanese Constitution would restrict Tokyo from taking a combat role.

“Japanese politicians and officials and most citizens know how important Taiwan is to Japan,” Newsham says. “But that hasn’t translated into deepened ties with Taiwan, and certainly not on the military front. The Japanese are still debating about whether it’s even legal to help the Americans if they defend Taiwan.”

International Christian University’s Nagy views Tokyo’s potential security cooperation with Taiwan as constrained in several ways. Besides the constitutional restriction on Japan’s right to use military force, operational capability is impaired by the lack of joint training with Taiwan and an insufficiency of military resources. In addition, legal and administrative arrangements that would be necessary for Japanese engagement have not been put in place.

The legal barriers could even prevent Japan from providing some indirect support to Taiwan. “Technically, the Chinese Civil War is still ongoing, and according to Japanese law, it is illegal to sell arms to states that are currently involved in conflict,” Nagy notes. “As a result, Japan is not legally able to sell arms to Taiwan.”

Newsham urges Washington and Tokyo to jointly draft an operational plan for a Taiwan scenario as soon as possible. He suggests creating a joint Japan-U.S. operational headquarters that oversees the defense of Japan and surrounding areas, including Taiwan. Without this type of command structure, in the event of a cross-Strait conflict, “we can expect to lose, or else to pay a much higher price than otherwise necessary,” he says.

He further urges much closer coordination among the militaries of the U.S., Japan, and Taiwan. “The Americans and Japanese need to immediately break Taiwan out of 40-plus years of isolation on the military front and start treating it like a friend and partner,” he says. “This needs to be priority number one.”