Geography does not favor only the attacker. Japan has its own territorial concerns: an assault on Taiwan could make smaller islands claimed by China appear more vulnerable. Some Japanese-held islands lie within roughly 70 miles, or 100 kilometres, of Taiwan. PAC-3 Patriot and Type 03 air defenses, anti-ship missiles, and sensors could observe Chinese movements, share data, or threaten aircraft and ships if Japan entered the fighting. China would still have to plan around those systems if Japan withheld fire but passed targeting information to Taiwan or its allies. Accidents, strikes on neighboring territory, or attacks on disputed islands could widen the conflict.
Chapter · 7:39-12:22
Japan's island chain complicates the Taiwan battlespace
Nearby Japanese islands add sensors, air defenses, anti-ship weapons, and escalation risks to a geography often reduced to Taiwan's proximity to China.