system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: do horses or other animals appearing in battle scenes in films/TV understand that they aren't actually in danger?
gpt
Horses have roughly the intelligence/mental capacity of a 3 year old and are engineered to be easily spooked. Battle horses would have to go through extensive training not to fear the battle scenario in general. 

Now that we have real battle out of the way, most TV show and movie filming is heavily doctored and the horses highly trained to execute what is needed for the filming. They know they are doing a trained job and there is no danger in general and the environment wouldn't really cause them to spook easily anyway.