Five groups give the Battle of Five Armies its name in J.R.R. Tolkien’s The Hobbit.
The battle takes place near the Lonely Mountain after the death of Smaug. The five armies are the Dwarves, Elves, Men, Goblins, and Wargs. In the story, the Dwarves, Elves, and Men initially stand against the Goblins and Wargs.
The conflict grows out of competing claims to the treasure of Erebor. Thorin Oakenshield has reclaimed the mountain, while Bard and the Elvenking seek a share of the wealth and compensation. The approaching Goblin and Warg forces transform the dispute into a larger alliance against a common enemy.
The Eagles and Beorn also intervene, but they are not counted among the five armies named in the battle’s title. This is the usual source of confusion when counting the participants.