French FDCs about World War I

On Friday I got a cover from France.

Stamp:

Maquis Barrage de l'Aigle (issued 05-09-2016)

with a special postmark from the philatelic shop in Boulogne-sur-Mer

Inside were two French First Day Covers.

Centenary of the Battle of Vimy Ridge (whole set) (issued 08-04-2017)
It is a joint issue with Canada.
The Battle of Vimy Ridge was fought in 1917 between the German Empire and the British Empire and is a part of the Battle of Arras. It was the first battle in which the four divisions of Canadian Expeditionary Force fought together. It ended with a victory of the British Empire. 

Centenary of the Battle of Chemin des Dames (whole set) (issued 14-04-2017)
The Battle of Chemin des Dames, also known as Second Battle of the Aisne, was fought between the German Empire and France in April and May 1917. The battle began as part of a meticulously planned Franco-British offensive, but had to be abandoned after many French divisions mutinied and ended with a tactical victory of the German Empire.

Thank You very much William!