It is sometimes claimed that ethnic nationalism emerged during the French Revolution. However, I consider this incorrect - in my opinion ethnic nationalism existed long before the French Revolution, while what emerged during that revolution was civic nationalism*. Let's remember that France prior to the Revolution was a multi-ethnic country with ethnic French people (i.e. speakers of French language) being just over 50% of the total population. Yet France did not fragment itself into several nation-states along ethno-linguistic boundaries, but remained unified, developing common French identity (even if separatists existed).
As the result, France is now the third largest country in Europe (after Russia and Ukraine). "Ethnic France" would have been smaller.
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*We can claim that it emerged during the Enlightenment in general, and was implemented in France, but also for example in the USA, in Italy, etc.