Well, we all have our predilections.
Personally, I'm inclined to go back to the late 16th century and talk about Hideyoshi's invasions of Korea, the Seven Year War, with the professed goal of conquering Ming Dynasty China.
Speculating about provocations to Japan in Neanderthal times would be fun too.
Just saying.
For access to northern China (aka Manchuria) - the "more modern day" Root-Takahira Agreement (executed 30 November 1908). To note in the Agreement are the comments on the Philippines (American real estate from the Apanish American War).
For Japan's support to the British Navy during WWI - those formerly held Pacific Islands by Germany - those that became known as the Mandates - went to Japan.
Also, a comparison of the Monroe Doctrine and the Stimson Doctrine might add other perspective here ... but, the ball is a'roundin'