I've been in enough movies to know that when you're on the set and you start shooting you're looking at playback and you get a sense of what it's going to be like.
I think you just assume that your memory is just sort of a video playback of your experience but it's nothing like that at all. It's a complete refabrication of an event and a lot of it is made up because you're filling in spaces.
It was quite a European war until 1917 when the Americans joined up. They don't have the same sense of the loss of innocence and the cataclysmic loss of life. A whole generation was wiped out.