


In the books, Thror was already killed by Azog 9 years prior to the battle, when he tried to enter Moria alone. In the film, Azog the Defiler kills Thror during the Battle at the gates of Moria, after which Thorin cuts off Azog's arm, assuming that the Orc later died of his wounds. The attack of Smaug on Erebor was not the only confrontation between Dwarfs and dragons the Dwarfs who had settled in Erebor had been driven away from their former homes by dragons almost 200 years before. A lot of background on many events in Middle-earth is described in The Hobbit, The Lord of the Rings and its appendages, as well as The Silmarillion and Unfinished Tales. In the beginning of the movie, it is stated that Bilbo's journey to Erebor started 60 years prior to his 111th birthday party. The Battle at the gates of Moria, seen in a flashback, took place in 2799 TA, 29 years after Thorin and his fellow Dwarfs were exiled from Erebor by Smaug (141 years prior to the start of An Unexpected Journey and 201 years prior to Fellowship). This is 170 years before Bilbo journeys with the Dwarfs to Erebor (2940 TA), and 230 years before Bilbo's 111th birthday party as seen in the beginning of The Fellowship of the Ring (3000 TA).

The prologue, showing Smaug's attack on Erebor and the city of Dale, took place in the year 2770 of the Third Age (TA).
