Thanks to all let me clarify. I should not apply our standards of language to what was used in war times. I was interested because of the talk about renaming modules, but MMP kept "Yanks" as that doesn't seem to be a sler. And if it was used as such it didn't carry much sting, because in WWI us Americans all sang a song that proudly proclaimed "The Yanks are coming, and we won't be back 'till it's over, over there"
So how did other nations soldiers refer to them-self's and/or how were they referred to by other combatants. I think that; again taking the Japanese; the use of Gaikokujin was probably who they referred to everyone else, Maybe calling europeans 'round eye's' or "hairi apes" was about as nasty as I can think they got, I just don't know.
I had forgot about the French, but I didn't think that "Poilus" was a insult. If so please enlighten me.
BTW: I think 'Yuri0352" is right about a "Sense of humor is a characteristic which in my opinion, would rarely if ever be associated with the members of the Imperial Japanese armed forces..."