My great great grandpa from my dads side is from Slovakia (back in the day Austria-Hungary so it was a same country) and my great grandpa from dads side was a bartender in Austrian hotel before WW1. My grandma from dad's side is from Austria and grandpa from dad's side is Slovenian.
My mothers side is Slovenian/Austro-Hungarian (Country I'm from) as far as I know. My great grandpa from mothers side fought for Austria-Hungary during WW1 and fell asleep and missed the battle. Later he found out from about 40 people only 2 survived. Grandma/Grandpa from mothers side are both Slovenian.
Non of them served in WW2 as far as I know (too young/too old)
My dad was in army during Civil War where Slovenia wanted their independence and other Yugoslav nations attacked us in 1991.
Well thats my background pretty much