Editor's note: Shao Xia is a special commentator on international affairs for CGTN. The article reflects the author's opinions and not necessarily the views of CGTN.

Why has China responded so strongly to recent remarks by Japanese Prime Minister Sanae Takaichi linking China's Taiwan to Japan's security?

The answer is straightforward: The Taiwan question is at the core of China's core interests and a red line that must never be crossed.

Takaichi has become the first sitting Japanese prime minister since the end of World War II to publicly suggest that a "Taiwan contingency" could be treated as a "survival-threatening situation" for Japan, a rhetoric that is widely seen as a threat and provocation to China. With this statement, Takaichi has committed at least three egregious mistakes.

Violating international law and post-war world order

Taiwan is an inalienable part of China. This is firmly grounded in history and law and has been recognized by the overwhelming majority of countries. This includes Japan upon its normalization of relations with the People's Republic of China (PRC).

Historical agreements such as the Cairo Declaration, the Potsdam Proclamation and Japan's own Instrument of Surrender all unequivocally confirm that Taiwan belongs to China. Japan has no legal basis to claim otherwise.

Japan, a defeated aggressor in World War II, now professes to have a so-called special relationship with Taiwan. This is nothing but a blatant disregard and violation of the post-war international order and international rule of law. It is akin to a thief who, after being ordered by the court to return stolen property, dares to claim "special feelings" for it and even threatens to use force against its rightful owner.

As a UN member state, Japan is obligated to uphold the UN Charter, which explicitly prohibits the threat or use of force against the territorial integrity of other nations. Any suggestion of armed intervention in Taiwan or any attempt to associate it with Japan's collective self-defense fundamentally violates Japan's post-war constitutional constraints.

It runs counter even to the peace and security legislation passed in 2015 by then Prime Minister Shinzo Abe's administration, reinterpreting Article 9 of Japan's constitution. The so-called collective self-defense legislation states that the use of force is permitted "when an armed attack against Japan occurs, or when an armed attack against a foreign country that is in a close relationship with Japan occurs."

However, Taiwan is NOT a country and Japan has no legal grounds to invoke the "collective self-defense right" regarding Taiwan.

The controversial legislation caused a huge outcry, both in Japan and abroad, for easing the restraints on deploying Japan's Self Defense Force.

Takaichi's rhetoric dangerously echoes the pretexts Japan used to justify its past aggression against China. If a nation can arbitrarily designate any issue a "survival-threatening situation," it would open a Pandora's box of unlimited intervention.

Breaching political commitments

Takaichi's remarks also by breach the one-China principle and the four political documents that underpin China-Japan relations. In the 1972 Joint Communique, Tokyo recognizes the PRC as the sole legal government of China and acknowledges that Taiwan is an inalienable part of it. These commitments are well documented and have served as the bedrock of normalized bilateral ties over the past decades.

Takaichi's track record of inflammatory actions on historical and territorial issues, from visits to the Yasukuni Shrine that honors war criminals to meeting Taiwan separatists, has long been a grave concern for Beijing. Despite this, China demonstrated goodwill by agreeing to a bilateral leaders' meeting at this year's Asia-Pacific Economic Cooperation forum.

Yet Takaichi reneged on Japan's commitments by meeting with the representative of the Taiwan authorities on the sidelines of the APEC meetings, a provocative step that has severely eroded mutual trust.

Provoking China will boomerang

This year marks the 80th anniversary of the victory of the Chinese People's War of Resistance Against Japanese Aggression and the World Anti-Fascist War. Yet, some Japanese politicians still refuse to apologize for their nation's past atrocities. And Takaichi has even gone so far as to provoke the Chinese people with the Taiwan question, which lies at the very heart of China's core interests.

Her reckless remarks also harm the interests of the Japanese people and businesses. Exports, tourism and cross-border investments that depend on stable China-Japan relations are all at stake.

What is most alarming is that Takaichi is pushing a broader, hardline defense agenda: massive increases in military spending, relaxation of arms-export restrictions, and pursuit of pre-emptive strike capabilities. These actions are prompting observers to ask whether Japan's true intention is militarization. Has Japan ever learned from history?

A former Japanese leader once remarked, "The smaller the dog, the louder it barks." While China has consistently responded with reason and kept its door open for genuine friendship, any politician who repeatedly betrays written commitments and threatens regional peace must be held accountable. They should never have any illusion about the collective will and unyielding resolve of the 1.4 billion Chinese people.

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