Japan as Taiwan’s Strategic Rear Front
Officially, there is no military alliance between Tokyo and Taipei. Japan does not have a defense treaty with Taiwan. It does not even have formal diplomatic relations with the island, its relations having been maintained at a “non-governmental” level since the 1972 Sino-Japanese communiqué. But, the strategic reality advances faster than diplomatic law. Japan’s foreign ministry now calls Taiwan an “extremely important partner” and a “precious friend,” sharing values like democracy, the rule of law, and fundamental rights with Japan.
This is where the formula becomes central: Taiwan is the advanced lock, Japan is the strategic depth. If Taiwan falls under Chinese pressure, Japan loses part of its geopolitical shield. If Japan withdraws from the Taiwanese game, Taiwan loses an essential part of its breathing space. The two are not legally allied, but they are already linked by a security equation.
Japan understands this. It is no longer content with cautious statements. It is preparing its south-western islands, strengthening its capacities, and considering civilian evacuations, infrastructure, ports, ferries, and means of transport. In March 2025, Tokyo presented a plan to evacuate more than 100,000 civilians from the nearby islands of Taiwan in case of regional conflict. This is not a declaration of war. It’s something else: the silent acknowledgment that the Taiwanese scenario has become a Japanese one.
For China, any convergence between Taiwan and Japan is a historical provocation, an attempt to encircle, and a possible internationalization of the Taiwanese issue. When Tokyo evokes a possible Japanese response in the event of a Chinese attack on Taiwan, Beijing understands that Taiwan is no longer just a Sino-Taiwanese confrontation, but a possible theater involving Japan and the United States. The novelty is that Japan is emerging from comfortable ambiguity: “‘a crisis in the strait could directly threaten Japanese security.'” The Japanese diplomatic Bluebook asserts that peace and stability in the Taiwan Strait are important not only for Japan’s security, but also for the stability of the entire international community. The more indispensable Japan becomes to Taiwan’s security, the more he becomes exposed himself.
So the paradox is clear: the more that Japan protects Taiwan indirectly, the greater its own vulnerability. BUT ,IF he doesn’t, he increases his future insecurity even more.
In reality, Tokyo and Taipei are already living in a de facto alliance. Not a signed alliance. Not a proclaimed one. Not an avowed alliance like NATO or the Japan-US treaty. But, an alliance through geography, semiconductors, shipping routes, democracy, the Chinese shadow and the American presence.
So the real question is no longer: will Japan defend Taiwan? The real question is: how far can Japan avoid recognizing that by defending its own security, it is already defending Taiwan?
Prime minister Shinzo Abe’s 2021 formula sums it all up: “ a Taiwan contingency would be a security emergency for Japan.” What was then a political statement is now becoming an operational reality. The non-treaty alliance is perhaps the most enduring form of alliance: it resists political change, Chinese pressure, and Trumpian uncertainty, because it rests not on signed promises but on geography, energy, and survival. Beijing knows this. And that is precisely why it worries about it.
