Japan’s Stance on Taiwan’s Security is Good for the Status Quo and Asian Security

On 7 October 2025, Japan’s new Prime Minister Sanae Takaichi livened up a House of Representatives Budget Committee meeting with an unexpectedly revealing response to a question posed by opposition Constitutional Democratic Party of Japan (CDP) representative and former Foreign Minister Katsuya Okada. A few years before coming to office, Takaichi had spoken of a Taiwan situation having the potential to develop in a way that threatens Japanese citizens and might require a response by Japan’s Self-Defence Forces. What, Okada wondered, did she think now?

Precise Wording

‘A judgment must be made after comprehensively assessing all information in line with the individual and specific circumstances of what has actually occurred . . . A line of private ships from China surrounding Taiwan would not constitute such a situation. If it involves the use of warships and armed force, it would be a survival threatening situation no matter how you look at it’ Takaichi responded.

By using the clunky term ‘survival threatening situation’, the PM had invoked the legal formula that marks the threshold for Japan to activate its right of collective self-defence even if not attacked itself. This right had been denied in post-war Japan until new legislation in 2015, and it is a line that has not been crossed in the intervening decade.

This matters far beyond any controversies it causes in Japan or between Japan and China, because of the extent to which Japan’s response would determine how a conflict involving Taiwan unfolds. The credibility of US deterrence against a forcible change to Taiwan’s status quo depends on the US military’s ability to project and sustain force in the region. That in turn depends on a host of air bases and ports across Japan, especially the US Marines in Okinawa, and the 7th fleet in Yokosuka. A recent tabletop exercise the author attended on Taiwan and the Indo-Pacific, organised by Centre for Security Diplomacy and Strategy (CSDS) at the Vrije Universiteit Brussel, presents a plausible scenario of how a conflict might play out. Assuming it doesn’t go nuclear, a Sino-US conflict over Taiwan is likely to settle into a protracted struggle with the PRC unable to safely get a critical mass of troops across the straits, and US forces unable to break a Chinese ‘blockade by fire’ (using ground-based missiles to prevent shipping arriving in Taiwan). Following the initial clash, the US runs low on munitions, and Japan becomes the indispensable staging post for replenishment, for attempting to bring in supplies to sustain the population and resistance on Taiwan, and for imposing a counter-blockade on the PRC.

Inside Japan, Takaichi was criticised for ‘reckless’ remarks, that were either insufficiently clear about the link between Taiwan and Japanese security (causing misunderstanding), or too specific (thus foregoing the advantage of strategic ambiguity), or risk a diplomatic ‘flashpoint’. Takaichi’s Defence Minister criticised the question on the basis that a determination would come down to the government using ‘all available information’ rather than the personal opinion of the Prime Minister of the day. The PM clarified that as she had been asked for her personal opinion, she was thinking of the ‘worst-case scenario’.

Statesmanship in China

China’s Consul General in Osaka tweeted over reports of Takaichi’s statement ‘the only thing to do is cut off a dirty neck without a moment’s hesitation. Are you ready for that?’ Chinese Foreign Ministry spokesperson Lin Jian accused Takaichi of ‘erroneous and dangerous remarks that attempt to separate Taiwan from China’s territory and advocate military intervention in the Taiwan Strait.’ Assuming the scenario is one where Japan’s ally the US is already in an armed conflict with China (rather than a unilateral intervention by Japan), this appears to misconstrue the kind of action Takaichi was talking about. Takaichi had mentioned that she was discussing just such a specific situation where ‘Taiwan comes under attack and warships blockade the island. In response, the US military moves to assist Taiwan, and to prevent that China attacks US forces.’ Considering the many academic studies and war games that envision a PRC attack on Taiwan opening with a pre-emptive strike on US forces in Japan, this is not an outlandish supposition. But neither that nor her reassurance on 10 November that she would refrain from making definitive statements about hypothetical cases did much to calm the voices of China’s Communist Party.

The PRC has taken a dim view of Takaichi for some time. Her views on war history (that Japan waged a ‘defensive war’ in Asia) are felt as insulting. In her 2021 interview on a Taiwan emergency she said ‘It would also be a threat to Japan. It could develop into a situation where we would not be able to protect the lives of our citizens. There is a high possibility that we would be forced to exercise our right of self-defense’. On becoming Prime Minister in 2025, Takaichi did not receive the customary congratulations from General Secretary Xi. Before the recent APEC summit, Takaichi tweeted that she ‘greeted and spoke with Lin Hsin-yi, Senior Adviser to Taiwan’s Office of the President.’ Use of Lin’s title drew a protest from China’s Foreign Ministry that the PM had gone against the ‘four political documents’ that form the foundation of China-Japan relations (specifically on not having ‘formal relations’). Following this latest controversy, PRC spokesman Lin Jian asked rhetorically ‘What signal is the Japanese leader trying to send to “Taiwan independence” separatist forces? Is Japan up to challenge China’s core interests and stop its reunification?’

The signal PM Takaichi is sending is one that badly needs to be heard, not primarily in Taiwan, but in Beijing. The short-term sacrifice of Sino-Japanese relations is justified by a need to avert a much larger danger, in other words, that Chinese hubris leads to miscalculation.

Director General of the German Marshall Fund’s Indo-Pacific Program, Bonnie Glaser recently assessed that her Chinese interlocutors are ‘exceptionally confident’, at this moment – ‘more than I have seen in my entire career of watching China’. Dennis Wilder (Initiative for US-China Dialogue on Global Issues at Georgetown University) shares Glaser’s worries that this could lead to greater aggression and miscalculation, adding that they accord with the notion that is dismissive of US power on the basis America is undergoing a ‘cultural revolution’. Wilder believes this (together with assumptions about the inevitability of China’s rise, the prevalence of the ‘East Wind over the West’) is leading to hubris on the Chinese side.

Such a Chinese tendency towards hubris is understandable. Japan’s 2025 defence white paper assesses the military balance between China and Taiwan is rapidly tilting in China’s favour. This summer General Secretary Xi Jinping presided over an ostentatious military parade in Beijing. He is rapidly expanding the nuclear force to get to parity with the US, and the PLA Navy has just commissioned its third aircraft carrier. Strategically, Xi probably feels he is in a strong position. Beijing’s relations with Moscow and Pyongyang are stable. The deal reached on 30 October in Busan appears to confirm China’s ability to face down President Trump’s tariff strategy. In the run up to those Xi-Trump talks, the President declined to approve a& transit by Taiwan’s President in July and a $440 million package of military aid in September. The last set of US-Taiwan military talks were downgraded. Xi did not feel the need to raise the topic of Taiwan at the Busan meeting.

The Dangers of Misinterpretation

There is a bloody legacy of hubris and miscalculation in Asia’s Cold War history. In the 1950s, North Korea’s leader (badly advised by communist block partners Stalin and Mao) misread US commitment to South Korea and invaded the South, expecting a rapid victory. It turned out President Truman was committed after all. The result was three devastating years of war. Any reassurance the North Vietnamese fighting to conquer the South might have felt on hearing President Lyndon B. Johnson’s campaign speech in Akron Ohio in 1964 was misplaced. Having pledged ‘we are not about to send American boys 9 or 10,000 miles away from home to do what Asian boys ought to be doing for themselves’, Johnson proceeded to deploy half a million US troops.

The most catastrophic scenario in Asia today would be one where a leader in Beijing who is insulated from sound advice becomes tempted to launch an attack on the mistaken assessment that Taiwan is isolated, and America and its allies won’t fight. Perhaps a similar a miscalculation gave Vladimir Putin hope for a quick war in 2022; such decisions happen when leaders are lulled by voices that whisper ‘you are much stronger, your opponent is isolated, and their allies won’t fight’. In hindsight, a well-aimed warning shot might have made all the difference.

It is therefore of paramount importance that well in advance of such a bad decision, somebody gets a message through the court circle surrounding authoritarian leaders and adjusts their cognitive frame. By signalling that Japan is ready to consider its role in a Taiwan crisis, PM Takaichi may have done just that.

Attempts have been made to transmit the signal at a lower volume for some time. Former Japanese Prime Ministers made statements to the effect that a Taiwan contingency is a contingency for Japan. In 2021, Taro Aso (then deputy Prime Minister) said Japan ‘would have to defend Taiwan’ with the US if the island is invaded by mainland China. As a former PM, Shinzo Abe said in the same year, ‘A Taiwan contingency is a contingency for Japan. In other words, it is also a contingency for the Japan-US alliance. People in Beijing, particularly President Xi Jinping, should not misjudge that.’ At the time, Takaichi said the Taiwan crisis scenario also presents a threat to Japan. ‘It can develop into a situation requiring defence of Japanese citizens’ lives, and there’s a high possibility it becomes a situation where the Self Defence Forces are mobilised.’

Takaichi has not changed the message, but she has turned up the volume. She has taken a leadership candidate’s personal opinion and expressed it as the stance of a Japanese Prime Minister at the dispatch box. She acknowledged the sensitivity of the issue, but did not retract her remarks. So far, it seems a well calibrated move. Things may yet develop for the worse, but to date China’s response (beyond fiery rhetoric) has been to advise its citizens against travel to Japan for tourism and academic study. According to an early poll, the Japanese public backs up the PM. She did not – indeed she cannot – make a commitment on behalf of Japan to intervene. However, in sharing her strategic assessment she has clarified that there need be no legal impediment to Japan’s activation of collective self-defence, depending on the general circumstances. Sanae Takaichi just fired a warning shot that everyone supporting the maintenance of the status quo on Taiwan and peace in Asia should be glad to hear.

© RUSI, 2025.

The views expressed in this Commentary are the authors', and do not represent those of RUSI or any other institution.

For terms of use, see Website Terms and Conditions of Use.

Have an idea for a Commentary you'd like to write for us? Send a short pitch to commentaries@rusi.org and we'll get back to you if it fits into our research interests. View full guidelines for contributors.