Through all of the struggles and challenges that the companions have faced on the quest to reclaim Erebor, from nearly being cut down by goblins in their dark tunnels underground to narrowly escaping becoming lunch for the giant spiders of Mirkwood, the group never knew if they would make it to the Lonely Mountain or not. So when they get there in one piece, none of them has given any thought about how they get themselves in, or get the sleeping dragon out.
After much difficulty involving the last light of the moon, and an ancient key that has been passed down from the forefathers of Thorin, they manage to get in and to wake the terrifying Smaug. In a rage, he flies out of the mountain, setting fire to the lands all around it, and then crashes into the stone in the side of the mountain in order to cause a rock slide. The dwarves are luckily inside the tunnel at the time, but they find that their way is completely barred, and that they cannot escape via the door they came through, and must instead journey deeper into the heart of the mountain to find another exit. The only problem is, they have no idea when Smaug will return, and they are afraid to go off exploring in tunnels in the dark under the knowledge that a fire-breathing dragon might come along at any second and smite them.
Subsequently, they find themselves trapped within the very halls that they were hoping to reclaim. Luckily for them, Smaug has his sights set on vengeance with the people of Lake Town, and has disappeared off to wreak havoc for the village on the water. The Master of Lake Town has fled with all of the money, his servant Alfrid is no better, screaming “every man for himself” and actively pushing people into harms way, which leaves Bard to be the only character brave enough to come in and deal with the problem. He shoots Smaug with a Black Arrow, right in a weak spot in the chest, and the dragon falls, solving all of the dwarves problems for them. However, the surviving people of the town, along with the elves of Mirkwood, then have a bone to pick with the dwarves in the mountain, and travel up there in order to demand the portion of the treasure that is rightfully theirs in the first place.
Thorin, of course, is having none of it, as he has succumbed to dragon-sickness at this point, but now the dwarves have a host of elves and men on their doorstep, so they are just as trapped inside the mountain as they were before. At this point, a highly unorthodox animal comes to their aid: Ravens. It turns out that the Lonely Mountain used to be known as Ravenhill, on account of the majestic and loyal birds who once thrived there. An old raven by the name of Carc was once a great friend of Thror, Thorin’s grandfather, when he was king under the mountain.
Thorin thus calls upon Roac, an equally old raven, who is the son of Carc, to honor the allegiance of ancient times, and help them in their plight. “If you will earn our thanks still more, bring us news of any that draw near. Also, I would beg of you, if any of you are still young and strong of wing, that you would send messages to our kin in the mountains in the north, both west from here and east. Go especially to my cousin Dain in the Ironhills, for he has many numbers, well-armed, and dwells not far from here.’
The ravens maintain the alliance with the dwarves over the next several days, taking messages back and forth about the comings and goings of the elves and men surrounding the entrance, and about how far away Dain and his dwarves are, thus whether or not they will be able to arrive in time to help. When Bilbo then offers up the Arkenstone, the heart of the mountain, the object of Thorin’s deepest desire to the ‘enemy’ in order to stop the needless war that is about to happen, the ravens speed quickly to Dain and urge him on, so that he gets there at exactly the perfect time to mess everything up with the agreement that is about to be made, but also to help fight the goblins and wolves that suddenly attack in the Battle of the Five Armies.
Birds and other animals have long been allies of the good people of Middle Earth, from the Giant eagles that swoop in and save the day, to the shape-shifting bear-man Beorn, and without them and their small acts of kindness, the story might have had a very different ending indeed.