I think the speed that the French Army of Paris were sent to the front ( Taxis and buses ) may have meant using the uniform you happened to be using at the time ! Paul
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The finest stories of the Great War are those that will never be told.
I think it's a pre-war photo pressed into wartime service by an enterprising postcard manufacturer. The infantry are wearing the linen "tenue d'exercice." Fatigues are "tenue de corvee." if this were a genuine wartime shot, I doubt that the men would have been in "tenue d'exercice," more likely tenue de route (or de marche or de campagne)
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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.
I tend to agree, James. I found the dress suspicious for war-time activity. One thing is certain, the French , more than any other people it seems, were gaga over photographs. Well over half my post card collection are of French origin.