The Playlist had previously reported that Eddie Redmayne ("The Good Shepherd") would be playing the lead role of Albert, but according to their sources, "Spielberg began to have second thoughts which led to more meetings and to the role eventually going elsewhere."
Irvine has worked with both the National Youth Theatre and the Royal Shakespeare Company, though his only screen appearance has been in the British TV series "Life Bites."
The international supporting cast includes Emily Watson, Peter Mullan, David Thewlis, Benedict Cumberbatch, David Kross, Rainer Bock, Nicolas Bro, Leonard Carow, Robert Emms, Patrick Kennedy, Cecile Buckens and "A Prophet" star Niels Arestrup.
Watson and Mullan will play Albert’s parents, while Cumberbatch will play the key character of Major Stewart. Additionally, Buckens will play a French girl who takes in Albert’s horse, Joey, and Arestrup will play her grandfather.
TheWrap previously broke the news that "Thor" star Tom Hiddleston would be joining the cast, and Empire confirms that he is officially in talks, along with explosive actor Stephen Graham ("This Is England").
DreamWorks’ "War Horse" gallops into theaters on Aug. 10, 2011.
Irvine’s casting was first reported on Empire Online.