It is an observation made by historian Tom Holland (see his new book Dominion) that the trenches of WW1 were everywhere filled with crosses. It is sure that some lost their faith in the trenches, but the surprising thing is how many didn’t, and even had belief confirmed. Tolkien, for example, seems never to have wavered in his belief.
Here is my review of the Sam Mendes film, 1917. I hope you enjoy: