There's two thousand years of China trying to dominate Indochina (Vietnam, Laos and Cambodia). As recently as 1979, Chinese army crossed into Vietnam with 50,000 Vietnamese dead in the end. As to the Japanese, the 20th century for recent experience.

As a friend in HKG says, "they get along as long as they are making money, take the money away and everybody in Asia will killing each other".

GF