China warned Japan may intervene militarily if it invades Taiwan

China has been warned to stay alert to the possibility Japan will intervene militarily in the event of an attack on Taiwan.

A research paper said recent gestures of support for the island indicate that Japan and the United States have been discussing the scenario and are making plans to deter Beijing from using force to take the island.

Although the Japanese constitution renounces the right to wage war, and the public may be reluctant to get involved in a conflict, the paper said there were at least three scenarios where a 2015 national security law authorised the Japanese Self Defence Forces to get involved – either by providing logistical support to the US, invoking a “collective defence” clause to join the US in defending the island or US bases in Japan coming under attack.

Beijing regards Taiwan as a breakaway province and has never renounced the use of force to reunite it with the mainland, but Japan would regard this as a significant threat to its national security and the regional political order.

The paper, written by Wu Huaizhong, a researcher with the Chinese Academy of Social Sciences, said that in recent years the Japanese government had hardened its stance.