Director Steven Spielberg knew how important the horse that went to war was in telling this story.
"The horse is the essential catalyst that allows this story to be told," Spielberg said. "But everybody has their moment from beginning to end, everybody takes center stage, nobody is upstaged by Joey, they're only complemented by Joey."
Spielberg chose unknown actor Jeremy Irvine as his film's young star and Irvine still can't get over it.
"I'm living on the moon. I'm kind of living in a very surreal world," Irvine said. "I need to get over the whole thing about watching yourself on screen, it's really weird. But I think a few more times of seeing it and I'll look at it with a bit of perspective."
The film's stars are all excited to be in a Spielberg movie, including two-time Oscar nominee Emily Watson, who met him early in her career.
"I just remember in the very early days of my career, just connecting with him and him shaking my hand and saying he'd enjoyed what I had done. And I remember I was speechless, like a goldfish with my mouth opening and shutting and I didn't know what to say," Watson said.
Actor Tom Hiddleston said he feels privileged to be in the film.
"I still feel just enormously privileged to play that very kind man that I play and to work with Mr. Spielberg and the other actors," he said.
Spielberg has horses on his property because his daughter, Destry, is an equestrian champion.
"War Horse" gallops into theaters on Christmas.