Here's a couple of golden oldies I remember enjoying, one of which (Richard III I think), has a real good battle scene, lots of mud, very realistic.
cut and paste from allmovie.com...
Henry V
Laurence Olivier's adaptation of Henry V is one of the finest Shakespeare films ever made, full of rousing action, beautiful colors and passionate performances. Henry V is the story of the newly crowned king of England who fights the French for possession of Normandy. Olivier's direction is inventive, beginning the film as if it were a performance at the Globe Theatre, and having it slowly expand so the final battle scenes take place in realistic settings. Released in 1944 during the height of World War II, Henry V didn't receive an American release until 1946, upon which Olivier won a special Academy Award for "his outstanding achievement as actor, producer and director in bringing Henry V to the screen."
Richard III
Laurence Olivier was the director, co-screenwriter (with Alan Dent), and star of this robust adaptation of Shakespeare's drama, which, as Bruce Eder has written, "was the final, crowning glory of the British studio system and the end of the great cycle of British films aimed at international audiences." Olivier begins his Richard III with Edward IV (Cedric Hardwicke) being crowned king. In the background of the celebration, Richard (Laurence Olivier) jealously views the proceedings. Soon afterwards, Edward IV is murdered, drowned in a vat of wine. Richard becomes king and, after proceeding with a succession of intrigues and duplicities, he finds his kingdom in dire peril, set upon by Henry Tudor (Stanley Baker) and mustering a final defense for his realm at the Battle of Bosworth.