Actually Siberia had lots of useful stuff. Oil is the biggest of the "stuff". Then you have the minerals. Most important might well have been space to allow colonists. The Japanese Army had occupied much of Siberia after WW I and had a good idea what was there.
What attracted the Japanese to the South was the extreme vulnerability of the European colonies. They wanted the Dutch Indies and Malaya very badly. The Philippines were done as a flank protection. The Japanese infiltrated all three areas, plus Burma and were able to place construction companies there. These had heavy equipment useful in Engineer units. Business contacts allowed much gathering of intelligence.
Pruitt, you are truly an expert! Kelt06
Have you been struck by the jawbone of an ASS lately?
by Khepesh "This is the logic of Pruitt"