What events led Japan to the 1973 war with China? Explain in one sentence

The 1973 war between Japan and China was not caused by a specific event, but rather, tensions had been building up over territorial disputes and historical grievances.

Did the league of nations have anything to do with it?

No, the League of Nations did not play a direct role in the 1973 war between Japan and China as it was dissolved in 1946 and replaced by the United Nations.