In the US, we don't seem to remember much about China's role in WW2, but something like 14 million Chinese died fighting Japan. US attention was obviously focused elsewhere. China's defense was actually important to our war with Japan. Japan is resource poor. If they would have gained access to China's resources many, many more Americans would have died. About 3% of the entire world's population died as a result of WW2. 75-80 million people died. Over half were civilians. Think about that.