The ongoing China-Japan dispute and diplomatic flare-up has just gone from bad to worse, and has taken a turn toward potential military confrontation. Japan’s defense minister, Shinjiro Koizumi, visited a Japanese island which has a military outpost that lies close to Taiwan on Sunday. The optics were unmistakable, signaling Tokyo doesn't plan on backing down after two weeks of Beijing demanding a retraction. It all started when earlier this month Japanese Prime Minister Sanae Takaichi made comments in a parliamentary meeting which made clear Japan could possibly intervene militarily in the scenario of China invading Taiwan.

"If there are battleships and the use of force, no matter how you think about it, it could constitute a survival-threatening situation," Takaichi had said, becoming the first Japanese top official in decades to link the Taiwan crisis to a potential Japanese military response. 

Beijing immediately embarked on punishing measures, including threatening trade relations alongside urging Chinese citizens to avoid all travel to Japan.

It was only last Friday that China again warned, "Prime Minister Takaichi's openly erroneous remarks concerning Taiwan have fundamentally undermined the political foundation of China-Japan relations and severely damaged bilateral economic and trade exchanges," according to the words of a foreign ministry spokesperson.

The following threat was emphasized, "Should the Japanese side persist on its course of action and continue down the wrong path, China will resolutely take the measures required and all consequences shall be borne by Japan." The United States is standing by Tokyo's side, even as the Trump admin appears to be sticking by the long-running Washington doctrine of 'strategic ambiguity' related to Taiwan's defense.

But instead of heeding the warning and reversing course, Japanese Defense Minister Koizumi unveiled the deployment of placing medium-range surface-to-air missiles on Yonaguni island.

"The deployment can help lower the chance of an armed attack on our country," Koizumi told reporters while sporting an military commander-style jacket. He also expressly rejected Beijing's concerns, though without invoking China directly. "The view that it will heighten regional tensions is not accurate," he said.

Importantly, the island in question - and thus the new highly provocative missiles deployment - lies just under 70 miles east of Taiwan. It looks to become part of a broader military build-up in Japan's southern island chain.

China has in turn already reacted to the development, saying Sunday: "Right-wing forces in Japan are ... leading Japan and the region toward disaster," foreign ministry spokesperson Mao Ning told a regular news briefing. Beijing "is determined and capable of safeguarding its national territorial sovereignty," she continued.

Various regional watchers are lining up on either side of the dispute, but nearly all of expressed surprise at Japan's new 'boldness'...

“The move is extremely dangerous and should raise serious concerns among nearby countries and the international community,” Mao added, also relating the whole spat back to PM Takaichi’s earlier remarks.

China has earlier warned Japan will suffer a "crushing" defeat if it ever decided to directly intervene in the Taiwan dispute. Recent years have also seen Beijing's anger grow after NATO briefly talked about opening an official office in Tokyo, but these plans were soon abandoned for the time being.