Why didnt Chairman Mao invade Japan?

In WWII Emperor Hirohito invade China for their Oil and resources, so why didn't Chairman Mao once he got to power and build up his army go to war with hirohito for what he done to China in WWII (some information might not be 100% accurate my history on Asia isn't the best, just correct me if i have made any mistakes then answer the question) Thank you ; - )