The Hobbit Chapter 15
From the lookout peak, the dwarves watch all night long. Thorin notices that all of the birds lingering are carrion birds. The old thrush appears again, and tries to speak to both Balin and Bilbo. They cannot understand him. Balin wishes aloud that the thrush were a raven. Dwarves used to use ravens to send messages. In exchange, the ravens lived in and around the mountain. Balin speaks of a Raven named Carc who led all of the other ravens and was very brave. The thrush cries out and then flies away. This confuses the dwarves, and they think that he is gone for good. He returns a little while later, leading an old raven behind him. This raven is Roac, and he is the son of Carc, the old raven. He tells them that he is over one hundred years old and is the chief of the remaining ravens. He adds that the thrush has given him news of Smaug's death. Thorin rejoices, but Roac warns that a host of elves and men are on the way to the mountain to claim some of the treasure for their own:
"'Your own wisdom must decide your course, but thirteen is a small remnant of the great folk of Durin that once dwelt here and now are scattered far. If you will listen to my counsel, you will not trust the Master of the Lake-men, but rather him that shot the dragon with his bow.'" Chapter 15, pages 257-8
Thorin is angry at the thought of surrendering or retreating, so he asks Roac to send messenger birds to his cousin Dain who can bring an army from a week or so away. Roac does not think that this is wise, but he obeys the dwarf. Thorin commands that they return to the mountain. Despite Bilbo's resistance, they return and begin to fortify the immense structures. Smaug had blocked up all entrances, except for the front gate. The dwarves immediately start cutting stone blocks and constructing a wall across the front gate. All the materials and tools they need are still in the mountain. The Ravens bring them periodic updates. Four days later, they see that the armies have approached. They have blocked the main gate and left a small arch for the stream. The mountain can only be entered from a narrow path on a ledge.
On the fifth night, they see the multiple fires of the elves and men in the ruins of the city of Dale below. They sleep little that night, and in the morning a company of elves and men make their way around the narrow pass. They are surprised to see the new wall, for they expected the dwarves to be dead. They leave and move the camp below the mountain. The next day, another company comes to the wall. Thorin calls out to them, and Bard hails them. He invites Thorin to come out and be part of a council with them. When Thorin refuses, Bard tells him that he killed Smaug and some of the treasure in the mountain that had been collected by the dragon, was from Dale. Thorin will not admit that they deserve a portion of the treasure for any reason. He tells them he will only give them money for the help that the city gave them, but will give no money as a result of force. He asks the group if they would have given his kin a portion of the treasure if they had found it. He swears that he will not bargain and tells them to go away. Bard tells him to think it over for a couple of hours.
When they return later, a speaker rephrases Bard's offer and Thorin shoots an arrow at him. They vow that they will not attack, but will not let them leave until they agree to bargain. Bard is counting on the fact that they cannot get supplies. All they have to eat is cram, but it will last a couple of weeks.