So Japan invaded China in the 1930's in order to establish an empire. Was China their only target or a stepping stone towards world domination?
During the 1930's China was a mess. The Nationalists (Chiang Kai-shek) had control (more or less) of most of the country. There wer warlords who had control of areas in the north. The communists had were based in Shaanxi province. There was fighting among them as Chiang tried to get complete control. The following would help. https://en.wikipedia.org/wiki/History_of_the_Communist_Party_of_China
How big is big enough for empire builders? Anything less than better/bigger than the British Empire would be second rate. There were some monumental egos at work there.
Agreed. But in a few instances, its aggression toward Korea seems to have been based on a fear of Asian powers - Korea being the obvious launchpad, as with the Mongol attempts.
Additionally, the "pie in the sky" dream was to add Australia and India to the Empire. Obviously unrealistic, but the dreamers loved the idea.
What were the Chinese Nationalists political ideas back during the 1930's? What were the Chinese Communists political ideas back during the 1930's?
I guess that when a country starts a military conquest they sometimes do not know when and where to stop.