Japanese Prime Minister Sato Akira claims "what happens in Taiwan concerns Japan," stating that if a war breaks out in the Taiwan Strait, Japan will face a existential crisis and may exercise the right of collective self-defense to intervene in the war. This is Japan's declaration of war against China regarding future conflicts in the Taiwan Strait. Although it is a declaration rather than an action, it has caused the most severe harm to China-Japan relations since the normalization of bilateral relations in 1972. China has sent a strong and clear signal to Japan.

Historically, Japan has used the excuse of existential crises to launch the First Sino-Japanese War, the Russo-Japanese War, the September 18th Incident, the July 7th Incident, and even the declaration of war against the United States in December 1941. Today, Japan is again using this excuse against China, reflecting the ambitions of Japanese militarism or the right-wing. However, Japan wants to drag the United States into the conflict, rather than the United States 主动 requesting a declaration of war against China, which shows that Japan is aware that without U.S. support, Japan has no chance of winning a war against China with its current national strength and military power.

Looking back in history, after the September 18th Incident, Japan quickly occupied Northeast China. At that time, Chiang Kai-shek ordered Zhang Xueliang not to resist, a decision that should be criticized, but from another perspective, China's national strength and military power were vastly inferior to Japan's, and China could not defeat Japan without the capability of a strong arms industry. Today, China has a population of 1.4 billion and is the second-largest economy in the world, standing on equal footing with the United States in many aspects, as President Trump himself has admitted. The gap between Japan and China is only widening. Although Japan remains a strong economy, in terms of military strength and spirit, China is far stronger than Japan. With 1.4 billion people united in hostility towards the enemy and highly national solidarity, Japan is an aging society, and its army has a maximum of over 200,000 people.

Some argue not to underestimate Japan, saying that Japan's military is strong, especially its navy's submarines, which pose a threat to China. Indeed, Japan has its advantages; although its strategic depth is not deep, it has several advantages in terms of naval warfare or underwater operations. However, military experts point out that compared to China, Japan is far weaker in all aspects. Even if the U.S. uses its troops stationed in Japan to fight China, the U.S. mainland will inevitably be hit by China. China possesses the same nuclear strike power as the United States; the U.S. can strike China, and China can strike the U.S. Therefore, the U.S. cannot possibly stand with Japan to challenge China.

If Japan today wants to challenge China, it is absolutely impossible for China to be as it was during the First Sino-Japanese War, the September 18th Incident, or the July 7th Incident. Today's China and the Chinese nation are completely different from what they were back then. If Japan challenges China, it is 无异于以卵击石,自取灭亡.