Border disputes in this area of the world meant your ancestors country of origin could change every few years. It makes it hard to know which nationality your ancestors actually were. For example, my great great grandmother is listed as being from Germany (1900, 1910), Prussia (1880) and France (1870, 1920) on US Federal census records. It all depended on the which country was controlling the area she was from the year the census was taken.
Prussia, German, or France? Where was she from?