Are you sure about this? Last time I checked the Japanese are not a Western power but an Eastern one. As to a peaceful China, they did invade Vietnam in 1979 (one of several times) they have had wars with the countries of Indo-China. China has certainly had its great empires which it won through wars of expansion. The Manchus did certainly invade many of its neighbors and incorporated them into the empire, i.e. Mongolia and even territory west of Xinjiang.
YOu need to relook at your history again. The military is a also a tool for the government to keep its people in order.