What happened when the eagles came to the battle of five armies in chapter 17

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."