Part of war propaganda is to assign a nickname to the enemy so as to dehumanize them. The USA has done this for decades in the wars in Southeast Asia, Vietnam, the Middle East, Central America, etc.
Did the Japanese soldiers refer to Western soldiers as "鬼畜米兵"?
Did the civilian population also refer to Western soldiers as "鬼畜米兵"?
Was there a slang term used by Japanese soldiers to refer to soldiers from Asian countries in WW2?