Speaking to Collider, the Thor actor, who stars alongside Benedict Cumberbatch and David Thewlis in the picture, said that the First World War film is soul-stirring.
Hiddleston declared: "I think the experience of the film is breathtaking. Just because it's a war film, it's about hope and courage and perseverance, set against the shocking waste of that particular war."
"That's the war in which Europe lost its innocence and lost a generation of young men. So many soldiers were killed."
The 30-year-old added: "Spielberg told me he's been looking for a story to tell about the First World War for a while, and then he saw the stage show and was moved beyond words by it and then later discovered in his research for the film that approximately nine million horses were killed in the First World War.
"In cavalry charges, as transportation, as ambulances. They literally worked every animal until they dropped down dead.
"And this story about one horse who is kind of our eyes is really about the durability and the courage of the human spirit."
War Horse opens in US cinemas on December 28 and on January 13, 2012 in the UK.
> First look: Steven Spielberg's War Horse
> Steven Spielberg 'frustrated with War Horse horses' acting
Watch the trailer for Steven Spielberg's War Horse below: