Although Japan has in recent months hinted it would aid in any Taiwanese defense against China, it would only help defend the island from Chinese attack if called on by the U.S. or if the conflict affected outlying islands under Japanese control, analysts say.
China claims sovereignty over Taiwan and has not ruled out the use of force to bring the island under its control.
Tokyo would join a U.S.-led defense of Taiwan because of its historical alliance with Washington, including the 70-year-old Japan-U.S. Security Treaty, experts say, or if China struck in a way that threatened Japan’s islets, such as Yonaguni, that are near Taiwan’s east coast.
An annual Japanese defense white paper in mid-July calls Taiwan important to domestic and international security for the first time, and it adds that “it is necessary that [Japan] pay close attention to the situation with a sense of crisis more than ever before.”
China retorted that Japan was interfering in Chinese internal affairs.
Chinese Foreign Affairs Ministry spokesperson Zhao Lijian told a press briefing, “Japan has been recently grossly interfering in China's internal affairs and making groundless accusations regarding China's normal national defense and military activities,” the official Xinhua News Agency reported.
Earlier in the month Japanese Deputy Prime Minister Taro Aso said the government would have to defend Taiwan with the United States in the event of an invasion, the Kyodo News Agency reported.
“It would not be too much to say that it could relate to a survival-threatening situation” if Taiwan ran into trouble, Aso said, as quoted by Kyodo.
Zhao, the Chinese Foreign Affairs Ministry spokesperson, called the remarks “extremely wrong and dangerous, as they … undermine the political foundation of China-Japan relations,” Xinhua reported.
Japanese State Minister of Defense Yasuhide Nakayama last month warned during a think tank speech that Sino-Russian collaboration could pose a threat and advised protecting Taiwan “as a democratic country.”
In April, U.S. President Joe Biden and Japanese Prime Minister Yoshihide Suga issued a statement saying both “underscore the importance of peace and stability in the Taiwan Strait.”
Japan’s Self-Defense Forces would move if a Chinese military campaign affected Japanese outlying islands, said Bonji Ohara, senior fellow with the Sasakawa Peace Foundation research group in Tokyo. Yonaguni is the closest to Taiwan, at 110 kilometers due east.
“If China tried to conduct [an] armed invasion upon Taiwan, China needs to conduct maritime blockade operation and also the air blockade operation,” Ohara said.
“The area of the blockade includes the Japanese territory like Yonaguni Island and also other islands in the southwest side of Japan,” he said.
Japanese forces would mobilize, especially if U.S. forces became involved at the same time, Ohara said.
Regular Chinese military flights in a corner of Taiwan’s air defense identification zone during the past eight months have sparked worries about a possible attack by China, which maintains the world’s third-strongest armed forces, after the United States and Russia. A 1979 U.S. law, the Taiwan Relations Act, allows the United States to help defend Taiwan militarily.
The Japan-U.S. Security Treaty commits Japan and the United States to act against common dangers. Both see Taiwan as a friendly Asia Pacific buffer against Chinese naval expansion.
Japan spars separately with China over sovereignty in parts of the sea between them and the two countries bicker about leftover World War II issues.
Tokyo would get involved if U.S. military planes or vessels were “under Chinese attack” or if Chinese missiles hit U.S. military bases in Japan, said Chen Yi-fan, assistant professor of diplomacy and international relations at Tamkang University in Taiwan.
“If the Taiwan Strait or its surrounding waters are under China’s control, Japan will have no choice but to respond,” Chen added.
However, Japan’s statements and movements since April by themselves do not signal intent to defend Taiwan in the event of an attack, some scholars say.
Tokyo’s comments amount to “shadow boxing” and “saber rattling” rather than intent to fight any war, said Jeffrey Kingston, a history instructor at the Japan campus of Temple University. Their statements help the government suggest to the Japanese public that it’s pursuing “values-based” foreign relations, he said.
“Nobody really believes it will come to a shooting war,” Kingston said. “It’s sort of a freebie for Japan to look tough, talk tough but knowing that at the end of the day it won’t actually be required to do anything.”
Aso’s comment, among others, reflects personal ideas rather than views of the Japanese government, said Huang Kwei-bo, vice dean of the international affairs college at National Chengchi University in Taipei.
“My feeling is that Japanese officials are always trying to dilute what these rather hawkish people are saying,” Huang said.
Suga said in April, for example, that his country would seek a "stable and constructive relationship" with China, Kyodo News reported.
Japanese officials hope to avoid irritating China now as they pursue post-pandemic economic recovery, Chen said. China is Japan's largest trading partner.