Finding language books and using them to build skill is a neat idea, as is allowing all PCs to know the basic phrases that the average tourist learns at the start of the campaign.
I know that in past wars, US soldiers (probably all Allied shoulders) were issued small, basic language guides for the country in which they would be operating (e.g. before D-Day, a lot of Allied troops were issued with French phrase booklets). I've never looked through one of those wartime language guides, but it stands to reason that some of the phrases contained therein would be of a martial nature (e.g. "Where are the German soldiers?"). I imagine that Allied forces would have started to issue Polish phrase books once NATO forces began their campaign there, and this probably would have continued at least until nuclear warfare began. That right there would be a justification for PCs to start being able to speak and understand basic Polish phrases.
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