This statement is repeated a few times by the narrator to enforce the idea China was attacked with no provocation by the Empire of Japan. To what extent is this statement true?
/u/PangeranDipanagara has an excellent write-up on China as a colonial, expansionist power in Southeast Asia. If you want to learn more, there is an entire FAQ on Chinese colonialism, talking more about China's inland expansions.
In short: China, an imperial power, has definitely attacked other civilizations.