China has urged its citizens not to travel to Japan and summoned the country’s ambassador in Beijing over Prime Minister Sanae Takaichi’s comments on Taiwan.

China and Japan have been locked in an escalating war of words this week, set off by Takaichi’s suggestion that Japan could respond with its own self-defence force if China attacked Taiwan.

Both countries’ foreign ministries have lodged serious protests with each other. A Chinese diplomat also made a comment which some interpreted as a threat to behead Takaichi.

The spat touches on the historical animosity between China and Japan, as well as longstanding “strategic ambiguity” on the sovereignty of self-governed Taiwan.

Here’s what else you need to know about it:

The current tensions were sparked at a parliamentary meeting in Japan last Friday, when an opposition lawmaker asked Takaichi what circumstances surrounding Taiwan would count as a survival-threatening situation for Japan.

“If there are battleships and the use of force, no matter how you think about it, it could constitute a survival-threatening situation,” Takaichi responded.

A “survival-threatening situation” is a legal term under Japan’s 2015 security law, referring to when an armed attack on its allies poses an existential threat to Japan. In such a situation, Japan’s self-defence forces can be activated to respond to the threat.

Takaichi’s remarks drew immediate ire from Beijing, with China’s foreign ministry describing them as “egregious”.

Last Saturday, Xue Jian, China’s consul general in the Japanese city of Osaka, reshared a news article about Takaichi’s parliamentary remarks on X. But he also added his own comment that “the dirty head that sticks itself in must be cut off”.

While the intent of Xue’s remarks “may not be clear”, they were “highly inappropriate”, Japan’s chief cabinet secretary Minoru Kihara told reporters on Monday.

Tokyo lodged protests with China over Xue’s remarks, while Beijing lodged its own with Japan over Takaichi’s.

Xue’s post has since been taken down – but the dust from the barbed exchanges hasn’t settled yet.

On Tuesday, Takaichi declined to retract her remarks, which she defended as “consistent with the government’s traditional position”. She did note, however, that she would be careful about commenting on specific scenarios from now on.

Then on Thursday, China’s foreign ministry posted in Japanese and English on its X account, warning Japan to “stop playing with fire” and added that it would be an “act of aggression” if Japan “dares to meddles in the cross-Strait situation”.

Chinese Vice Foreign Minister Sun Weidong also summoned the Japanese ambassador to China that same day to express their unhappiness.

Sun called Takaichi’s remarks “extremely wrong and dangerous” and demanded that Japan withdraw the comments, according to state media Xinhua. He also warned that “otherwise all consequences must be borne by Japan”.

Japan’s ambassador explained that their position on Taiwan “has not changed” and refuted Beijing’s remarks, Chief Cabinet Secretary Minoru Kihara told reporters on Friday.

“It is the consistent position of the Japanese government that we hope for a peaceful resolution of issues surrounding Taiwan through dialogue,” he said during the daily news briefing.

Kihara also added that Japan “strongly urged China to take appropriate action” over Xue’s social media comment.

Then on Friday night, the Chinese embassy in Japan published a statement urging citizens “to avoid traveling to Japan in the near future” over what it called “blatantly provocative remarks regarding Taiwan”.

There is longstanding animosity between the two countries, which can be traced back to a series of armed conflicts in the 1800s and Japan’s brutal military campaign in China during World War Two.

This was referenced in a statement released by China’s Ministry of Foreign Affairs on Thursday when it said that “should Japan fail to draw lessons from history and dare to take reckless risks, even resorting to military intervention in the Taiwan Strait situation, it will inevitably suffer heavy losses and pay a bitter price in the face of the iron wall of the Chinese People’s Liberation Army”.

Historical grievances have remained sore spots in bilateral relations ever since. But the recent ascension of Takaichi, a protégé of the late former prime minister Shinzo Abe, suggests more tensions may lie ahead.

The conservative leader is pursuing closer ties with the US and has pledged to increase Japan’s defence spending – raising some alarm in Beijing.

Takaichi is also famously hawkish on China and a longtime supporter of Taiwan.

She had previously said that a blockade of the island could threaten Japan, and that Japan could mobilise its troops to stop a Chinese invasion.

China is especially touchy about Taiwan, the self-governed island that Beijing claims as part of its territory. China has not ruled out the use of force to take Taiwan – a posture that has unsettled Taipei and its allies in the region.

Earlier this month, Beijing accused Takaichi of violating the one-China principle, after she posted photos of herself meeting a senior Taiwanese official on the sidelines of the Apec summit in South Korea.

The Japanese prime minister’s recent comments mark a departure from the equivocal position that the country has traditionally adopted on the status of Taiwan.

This is in line with the policy of “strategic ambiguity” that the US has long maintained: remaining vague about what it would do to defend Taiwan in the event of a Chinese invasion.

For decades, this ambiguity has kept China guessing – a form of deterrence – while leaving room for economic ties to flourish.

The Japanese government’s official stance is that it hopes the Taiwan issue can be resolved peacefully through dialogue – and Japanese officials have typically avoided mentioning Taiwan in public discussions about security.

On the occasions where they have, they have been met with sharp rebuke from Beijing.

In 2021, when then deputy prime minister Taro Aso said that Japan would need to defend Taiwan alongside the US in the event of an invasion, Beijing condemned his remarks and told Japan to “correct its mistakes”.

In this more recent flare-up, China’s foreign ministry said that Takaichi’s remarks were “a gross interference in China’s internal affairs”.

“Taiwan is China’s Taiwan,” ministry spokesperson Lin Jian told a press briefing on Monday, adding that China would not “tolerate any foreign interference” on the matter.

“What signal is the Japanese leader trying to send to ‘Taiwan independence’ separatist forces?” he added. “Is Japan up to challenge China’s core interests and stop its reunification?”