Director Steven Spielberg stated that the only digital effects used in the movie were three shots that lasted three seconds, and it was done to ensure the safety of the horse involved. Spielberg was quoted as saying, "That's the thing I'm most proud of. Everything you see on screen really happened."
When Joey is trapped in barbed wire, the wire used was rubber prop wire when a real horse was used. Part of the filming of this sequence utilized an animatronic horse.
Fourteen horses played Joey during the movie. The main acting horse in the film, Finder's Key, also portrayed Pur sang: la légende de Seabiscuit (2003) in the eponymous movie about the famous racehorse.
Author Michael Morpurgo's original 1982 book "War Horse" evolved from chance meetings with three surviving WWI soldiers in Iddesleigh, Devon, Morpurgo's English hometown. After a number of meetings with the former members of the Devon yeomanry, and consultations with the Imperial War Museums (IWM), Morpurgo was able to write a story based on the experiences of the veterans and their poignant accounts of, not just human slaughter on the battlefield, but also the wholesale carnage and starvation of horses.
Lead actor Jeremy Irvine had never ridden a horse prior to being cast in this film, and this was his very first feature film.
Michael Morpurgo: The author of the source book is seen standing next to David Thewlis during the auction scene at the beginning of the movie. Morpurgo's wife Clare is also seen in the film.
Steven Spielberg: [fathers] Albert's father is the initial antagonist who deprives Albert of his best friend by selling Joey into danger.