Background Timeline to The Hobbit

In the book(s), as show here, the investigation of the true nature of the Necromancer takes place over more than a thousand years. Gandalf visits Dol Guldur multiple times over centuries before establishing that the Necromancer is Sauron in 2850, 90 years before The Hobbit.

In the film, it's Radagast that enters Dol Guldur and discovers the morgul blade and that happens at the same time as the journey to Erebor by Thorin's company is taking place. I think this would make it impossible now to show a flashback of Thráin's imprisonment and how Gandalf gets the map and key to Erebor's secret entrance.

The other deviation from the timeline is that, in the film, Azog is not killed but survives, likely with much of the actions of his son, Bolg, in the books being taken over in the films by Azog himself.

But here's a hopefully useful timeline for viewers of An Unexpected Journey of what "really" went down.

c.1100

• The Wise (the wizards and senior elves) discover an evil power known as the Necromancer has built a fortress at Dol Guldur. They suspect it to be one of the Nazgul.

1999

• The dwarf Thráin I comes to Erebor (the Lonely Mountain) and founds a kingdom.

2060

• The power of Dol Guldur grows and the Wise fear the Necromancer may be Sauron taking shape again.

2063

• Gandalf goes to investigate Dol Guldur but Sauron retreats to the east and avoids detection.

2460

• Sauron returns to Dol Guldur.

2463

• The Wise form the White Council to monitor the growing concern about the threat of Dol Guldur.
  • [a much later meeting of the White Council is portrayed in the film with Saruman, Gandalf, Galadriel and Elrond in attendance]
• Sméagol (later known as Gollum) obtains the One Ring.
  • [this is show in a flashback in the Lord of the Rings films]

2470

• Sméagol/Gollum hides in the Misty Mountains.

2770

• The dragon Smaug attacks Erebor (the Lonely Mountain) and takes the kingdom.
  • [this is shown in the "prologue" flashback of An Unexpected Journey]
• The King, Thrór escapes with his son Thráin II and grandson Thorin II (later known as Thorin Oakenshield).
  • [this is also shown in the prologue of An Unexpected Journey]
• Thráin II has a map and key to a secret entrance to Erebor.

2790

• Thrór goes to Moria where he is killed and beheaded by the orc Azog.
  • [this is portrayed via a flashback recounted by Thorin II in An Unexpected Journey]
• The dwarves declare war on the orcs and Azog is beheaded by Dáin.
  • [in An Unexpected Journey, Azog just has his arm cut off by Thorin II and survives. The Jackson films seem like they'll merge Azog with his son, Bolg]

2841

• Thráin II tries to go back to Erebor but is pursued by Sauron's forces.

2845

• Thráin II is captured by Sauron's forces and imprisoned in Dol Guldur.

2850

• Gandalf enters Dol Guldur and confirms the Necromancer is Sauron.
• He also discovers Thráin II in prison there and, before dying, Thráin II gives Gandalf a map and key to the Lonely Mountain to give to his son, Thorin II.

2851

• Gandalf presses the White Council to attack Dol Guldur but Saruman is against the move (as he is secretly wanting Sauron to rise in power in the hope it would reveal the location of the One Ring)

2941

• Gandalf is concerned what would happen if Smaug were to be used in the service of Sauron.
• Gandalf meets Thorin Oakenshield in Bree and realizes he is the heir of Thráin II.
• Gandalf gives Thorin the map and key and agrees to help Thorin reclaim Erebor.