I do not know if the doctrine that the nation-state arose in...

I do not know if the doctrine that the nation-state arose in the 19th century was still being taught:;... but it is erroneous. The nation-state reaches back far into the origins of Europe itself and perhaps beyond. If Europe was not always a Europe of nations, it was always a Europe in which nations existed, and were taken for granted, as a basic form of the State.