What are the possible effects of the author's choice to use an animal's narrative perspective to tell a story about World War 1 in War Horse?

Animals resonate with readers and the very sympathetic Joey certainly connects with people's sympathies. Horses do not belong anywhere near war. They belong on peaceful trails, fields, stables....but certainly not among bullets, blood, and violent noise. Joey is a very sympathetic protagonist and, being a horse, connects readers with the peace that horses represent. The author juxtaposes this peace with the senseless violence wielded by man.