Before Peter Jackson took the reigns of the franchise, Guillermo del Toro was supposed to direct The Hobbit, and planned to bring his friend and longtime collaborator Ron Perlman to voice the dragon Smaug. But financial problems at MGM eventually forced del Toro from the project; after Peter Jackson, king of The Lord of the Rings, signed on to direct in his place, he replaced Perlman with Benedict Cumberbatch.
Actually, The Hobbit wasn’t originally planned as a trilogy; as first conceived by Jackson and his collaborators, J.R.R. Tolkien’s novel would have served as the basis for a pair of films; An Unexpected Journey and There and Back Again. During production, it was decided to expand the two-part franchise into a three-parter, with The Desolation of Smaug inserted between Journey and Back Again (whose title was later changed to The Battle of the Five Armies)
Watch this video to find out more about the unexpected journey behind the scenes of the first film in The Hobbit trilogy: