The video below has some interesting comments about cavalry and how they are depicted in movies as opposed to the reality. It’s focus is on the use of cavalry in Ancient and Medieval times but still bears some validity to the First World War period. Naturally, the biggest issue is that in reality, the horse made for a large target that was readily attacked by the enemy. But this can’t be readily depicted in film since they are not actually trying to kill the horses (in theory, anyway). It’s worth a listen.