Something I never hear about during WWII is how the different allied forces got on with each other. Not the higher ups but the boots on ground. How did the regular soldiers interact with their allies.
How did the American troops get on with their British counterparts? How did Germans get on with the Italians? British and Canadians? Honestly the list can go on. There has got to be some first hand accounts of these interactions.
I served with the US army in Basrah, or Basra or however you want to spell it, Iraq in 2009 shortly after the British handed over operational command over to us so we still had a number of British liaisons. I know the liaison assigned to us was awesome and my unit got along with her really well, but I will say there were a number of things that were alien, for lack of a better term, to us. How they saluted (palm out instead of our palm down) how they carried their weapons and the different slang terms of turn of phrase. There were some, though not all, that referred to America as "the colonies." Honestly, I don't know if this was derogatory or just how America is referred to in casual speak.
I won't lie, all too often when I saw two British soldiers talking between themselves and I could not understand a word they were saying, so even though we speak the same language there was still a barrier there. I wonder if the interaction between allied troops in WWII were the similar or something else entirely. Went off on a bit of a tangent there, but it would make for an interesting topic I think.