Wildly off-topic, but this absolutely fascinating history of the French language http://www.realfrench.net/pdf/origins.pdf includes the following reference to the Great War:
Despite the introduction of primary schools (in which standard French was taught), most people continued to use regional dialects during the 19th century. It was not until the First World War that the tide began to turn away from regional dialects and towards the national language. Because of the appalling losses experienced during the first battles, units originally formed along regional lines were reformed, taking in soldiers from every part of France. As a result, soldiers tended to use French to communicate, and this trend continued in post-war life. With fathers speaking French at home, draconian punishments for children who used dialects at school and the development of mass media and publishing, it was not long before French achieved the universal status that it enjoys today.
I'd heard that at the time of Waterloo only around 10% of French people spoke French, and this seems to bear that out. I didn't know that that was still the case to some extent into the 20th century. Also, as in the case of the British "Pals," the French scrapped localised recruiting in order to spread the risk.
Just found it v interesting.
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"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.
This was also the case in Germany many "Germans" spoke regional dialects exclusively, my wife tells me that her Great Grand parents only spoke the local dialect which is how she learned it and as a child.... I think the situation was much the same...
I heard that the same happened in Italy at the turn of the XIXth century! In fact I knew an immigrant old lady who never learned much Spanish after living here for 60+ years... and was always badgering us in some impossible Sicilian dialect! We should have stayed off her garden, but our football always landed there!