I don't know about the demographic claim but definitely the French could not imagine _fighting_ another war and so their preparations were poor. They built the

I don't know about the demographic claim but definitely the French could not imagine _fighting_ another war and so their preparations were poor. They built the Maginot Line as a way of avoiding having to fight again. And I believe the political culture in the country and army all rotated around the idea that they never wanted to fight Germany again. This also extended to the Treat of Versailles were they tried to cripple Germany's ability to raise an army again. I don't know about the demographic claim, but he is sort of right that WW1 wrecked Frances fighting spirit.