Thorin notices that there are huge flocks of birds flying to the mountain. Something strange is happening.
The old thrush appears and keeps singing meaningfully at them.
None of them can understand, but Thorin mentions that he can follow the speech of the ravens.
So the thrush flies off and comes back with an ancient raven, Roäc.
Roäc explains that Smaug has been killed (yay!).
But, "many are gathering hither besides the birds" (15.19).
The elves are marching to the Lonely Mountain in hopes of gaining a share of the treasure.
And the Lake-men aren't too happy with the dwarves. They want some cash to rebuild their town.
Thorin sends Roäc to bring all this news to his cousin, Dain. The dwarves need reinforcements.
The dwarves return to the mountain and block off as many gates as they can to prepare for war.
The dwarves are feeling braver and braver: even though there are only thirteen of them (well, plus one hobbit), they're fighting from their old home.
Also, they now have tons of treasure – that would make anybody feel better about things.
The elvish and human armies eventually arrive to camp in front of the Lonely Mountain.
The dwarves sing their song with a new, inspiring twist: "The king is come unto his hall / Under the Mountain dark and tall / The Worm of Dread is slain and dead, / And ever so our foes shall fall!" (15.35).
Bilbo is starting to feel really depressed: all of the dwarves' talk is so warlike.
The next day, Bard of Lake-town goes to address Thorin.
He reminds Thorin that Lake-town has been destroyed in part because Thorin got Smaug all riled up.
What's more, it was Bard who shot the arrow to destroy the dragon.
So doesn't Thorin owe the men of Lake-town a little something?
Thorin admits that there is some truth to this.
Still, he won't negotiate with an army on his doorstep.
And Thorin especially won't negotiate while the Elvenking is nearby – he hates that guy.
Bard replies, "The Elvenking is my friend, and he has succoured the people of the Lake in their need, though they have no claim of friendship on him" (15.47).
In other words, unlike you, Thorin, the Elvenking has helped us out now that our whole town has been crushed under a dragon corpse.
Then, the armies of the Lake-men announce that the Lonely Mountain is under siege. They won't actively attack the dwarves, but they won't let them leave without giving the Lake-men a portion of their gold first.