Battle of the Five Armies
Now that Erebor has been reclaimed, all eyes turn to the mountain.
The Men of Lake-Town
The people of Lake-Town abandoned their town to go to the mountain, hoping for their fair share of the treasure within.
The Elves of Mirkwood
The elves from Mirkwood, who had heard of the company's good fortune, left the forest to come get their share of treasure. The elf king, Thranduil, had treasure of his own in the mountain, that he had given to the old dwarf king, Thror, before the dragon had come.
The Lord of the Iron Hills
Bilbo and the dwarves barricade themselves inside the mountain. Thorin, the leader, is obsessed with his new wealth, and refuses to part with any of it to the elves of Mirkwood or to the people of Lake-Town. As winter closes in, the men and elves lay siege to the mountain.
Thorin sends a message to his cousin, Dain Ironfoot, Lord of the Iron Hills, about his plight, and calling for help. Dain and his army set out immediately for the Lonely Mountain.
Goblins from the Misty Mountains
The elves from Mirkwood weren't the only ones who heard about the end of Smaug's reign: the goblins in the caves under the Misty Mountains heard as well. Driven by greed, they rush to the mountain. Just as the Dain Ironfoot arrives and is about to do battle with the combined armies of humans and elves, the horde of goblins appears. Thorin and the rest of his company join Dain and the three armies join together to fight off the goblins.
The Eagles
The men, elves, and dwarves are fighting bravely, but the overwhelming numbers of goblins are taking their toll. As the battle seems lost, Gandalf appears with giant eagles. The eagles swoop in and decimate the goblins, bringing a quick end to the battle.
The Aftermath
After the battle, the humans, dwarves, and elves are all friendly again, and the dwarves gladly give them their share of the treasure. Bilbo takes his 1/14 share of the treasure and returns to his home in the Shire, where he lives out the rest of his life in a much more exciting way than many other hobbits do.