But when did this photographic habit arrive?
No one knows.
And what does it have to do with the Western Front?
Check out this Poilu ribbing his officer.
We are always presented with dreary scenes on the Western Front but this story shows that despite all the squalor surrounding them, despite all the danger just over the trench parapet, the poilu never lost his sense of humour.
Vaya con Dios my good man.
Although by the grimace on the officer's face, we can only speculate that he is thinking: "Good grief, not another one! I thought they got over this. Oh well, must endure this for the home front. Just think of France and it will be done. Vive la France!"