~1.3 billion to ~130 million and shrinking. Why fear a 10x smaller neighbor?
You have no idea about the Japanese military. In a one-to-one battle, Japan will beat the Chinese hands down. The Japanese Air Force and Navy is much more superior than that of the PLA. And the Chinese Army, at the best can match their Japanese counterparts. Japan has some of the most advanced weapons in the world, while China produces cheap copycats after stealing Russian technology.
You should update your information because they are atleast 10-15 years old.
China doesnt only have the quantity they are modernizing their military by a ridiculous speed in the past 15 years.
For example their submarines are on par with germans which are the best in the world.
China is without doubt the central super power in SEA.
And im just talking about conventional weapons not even nuclear (which japan doesnt have).
There is no way japan could win a 1on1.
All that isnt suprising if you just look at the military budget of the respective nations (2014):
1. Usa ~600 billion
2. China ~200 billion
3. Russia ~80 billion
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9. Japan ~40 billion