The recent statement made in parliament by Japanese Prime Minister Sanae Takaichi marks a potential turning point in East Asian security dynamics.

Takaichi's remarks that a Taiwan contingency involving the use of force could constitute a "survival-threatening situation" for Japan mark the first instance in which Japan has explicitly applied the legal grounds for exercising collective self-defense, established through 2015 security legislation, to the Taiwan question.

This can easily be interpreted as a grave provocation, directly challenging China's "red line", which considers external intervention in the Taiwan question as an act of intervention in its internal affairs and a critical violation of its core interests.

It is noteworthy that Takaichi has stated that she will not retract her remarks despite the controversy. This appears to be not just a personal opinion, but a deliberate public unveiling of an intervention scenario in the event of a Taiwan contingency, which the Japanese government has been preparing for covertly.

A "situation of existential threat" refers to a legal concept that allows Japan to exercise collective self-defense in situations that it thinks significantly affect the peace and security of the country, enabling it to deter armed attacks against Japan or against its allied countries.

While Japan officially recognizes Taiwan as part of China, and not a country, the inclusion of a "Taiwan contingency" here indicates that a conflict over China's Taiwan could be defined as a "survival-threatening situation" for Japan.

This opens the door for Japan's Self-Defense Forces to engage in military operations alongside United States forces, extending beyond logistical support. It also signals, both domestically and internationally, that Japan views its operational integration with the US as now including the Taiwan Strait.

Takaichi, expressing concern over the deterioration of Japan-China relations, said she would "refrain from making comments based on specific scenarios". However, the fundamental essence of her statement was not retracted.

This represents Japan's delicate balancing act between strategic hedging and strategic clarification.

China regards the Taiwan question as its top core interest and has strongly opposed any possible Japanese intervention in the Taiwan question, viewing such involvement as interference in its internal affairs.

The remarks made by Takaichi appear to primarily aim to test the boundaries of China's tolerance. However, her continued insistence on upholding these statements demonstrates Japan's determination to directly link the stability of the Taiwan Strait to its own national interests, thus indicating a shift away from its previous strategic ambiguity.

Although Japan has pledged to "exercise restraint" in its rhetoric due to diplomatic considerations for China, its strategic stance has been maintained.

The security situation in East Asia is currently experiencing a structural shift.

China is accelerating the modernization of its military capabilities, which expands its regional influence, while the US is realigning its alliance network and strengthening its deterrent posture.

Amid this redistribution of power, middle powers such as Japan are compelled to adjust their diplomatic and security strategies in a multifaceted manner.

As a result, these remarks cannot be brushed off as a mere mistake by one politician, because they align with the recent trend of emphasizing the "importance of peace and stability in the Taiwan Strait", as repeatedly underscored in joint US-Japan statements and during the two sides' Security Consultative Committee (2+2) meetings.

The US, as part of its "Indo-Pacific" strategy, views Japan as a key pillar in countering China's military influence, with the Taiwan question being the most vulnerable link in its integrated deterrence strategy.

Takaichi's statement thus serves as an indication that the US-Japan alliance has effectively formalized a joint response to a "Taiwan contingency".

Her statement is an irresponsible comment that fundamentally undermines the security of Northeast Asia.

The Taiwan question is based on the one-China principle, which has long been acknowledged by the international community, including Japan. Remarks from a leader disregarding this principle are detrimental not only to Japan but also to the trust and stability of the entire Asia region.

Furthermore, effective multilateral diplomacy requires leadership that is grounded in reality and principle and makes statements cautiously.

A single statement from a nation's top leader can simultaneously create repercussions in the areas of economy, security and diplomacy.

Takaichi's statements, along with her refusal to retract them, symbolically represent Japan's full shift from its long-standing security policy of an exclusively defense-oriented framework to one of active collective security that forms more proactive engagement in regional instability.

East Asia's geopolitical landscape has become more unpredictable largely due to this strategic clarity of Japan's diplomacy. It is now crucial to conduct a comprehensive analysis of the regional consequences resulting from Japan's redefined military stance to assess the geopolitical prospects in the region.

The author is chairman of the South Korean civil group Korea-China Exchange Promotion Committee.

The views do not necessarily reflect those of China Daily.