 Medieval Germans migrated eastwards during the medieval period Ostsiedlung until the flight, evacuation and expulsion of Germans after World War II; many areas in Central and Eastern Europe had an ethnic German population.In the Middle Age, Germans were invited to migrate to Poland and the central and eastern regions of the German Holy Roman Empire and also the Kingdom of Hungary following the Mongol invasions of the 12th century, and then once again during the late 17th century after the Austrian-Ottoman wars to set up farms and repopulate the eastern regions of the Austrian Empire and Balkans.The Nazi government termed such ethnic Germans "Volksdeutsche", regardless of how long they had been residents of other countries.