At the end of the chapter, Gandalf appears and says "Well done, Mr Baggins," adding, "There is always more about you than anyone expects." Gandalf says that there is an unpleasant time just ahead, but after that Bilbo will be in a much better condition. Analysis:

The title of the chapter comes from a Biblical parable that describes the transactions of justice and Divine judgment as occurring as quickly and suddenly as a "thief in the night;" accordingly, one should always be on guard. What we find in this brief chapter is the elevation of Bilbo to a pacifist/Christian hero, who receives the paternal blessing "Well done..." as opposed to the more martial, Anglo-Saxon hero. The Arkenstone comes to symbolize a sacrifice on Bilbo's part, and as the heart of the mountain, it is also a symbol of the gifts passed on as legacies and heirlooms. Bilbo's character development and his burglary in particular, represents a re-assignment of blessings and gifts without regards to history, lineage or tradition. This is another contrast between the pagan and Christian traditions that Tolkien seeks to merge in The Hobbit. Chapter Seventeen: The Clouds Burst

Trumpets blare and there is going to be war. Dain, the cousin of Thorin, has arrived with soldiers and supplies. Bard approaches the mountain and offers the Arkenstone in exchange for peace and a fair share of the mountain's treasure. Thorin turns on the hobbit and attacks him, saying "I wish I had Gandalf here! Curse him for his choice of you!" Gandalf appears and defends both himself and Bilbo. Bilbo leaves, relinquishing his share of the treasure, counting it as the Arkenstone. Thorin is thinking of ways to avoid a fair bargain and when battle erupts, it includes men, elves and dwarves. They are ready to attack one another until Gandalf announces the approach of the Goblins, bats, wolves and Wargs. The armies re-align themselves and conduct what became known as the "Battle of Five Armies." The Goblins and Wild Wolves battle against the Elves, Men and Dwarves. Gandalf has expected some sort of assault but it did come swifter than he had expected. The Goblins are initially repelled and ambushed by the Elves, but a reinforcement of Goblin troops tilts the balance of the battle. It is only with the final arrival of the Eagles, that the forces of good are sustained. Unfortunately, Bilbo is "smote" with a "stone hurtling from above...and he fell with a crash and knew no more."
Analysis:

This is the one major battle scene of the novel and while we make numerous comparisons between this war and events of human history, the most important thing to grasp is that this is a polarized struggle between good and evil.