From The Lord of the Rings wiki
Battle of the Five Armies
The Battle of the Five Armies was a pivotal conflict fought at the Lonely Mountain that saw the forces of Men, Elves, and Dwarves unite against an invading army of Goblins and Wargs.
Overview
The battle occurred at the end of the quest to reclaim Erebor, triggered by the death of Smaug the Dragon. As the treasure of the mountain lay unguarded, tensions rose between the Men of Lake-town, the Elves of Mirkwood, and the Dwarves under Thorin Oakenshield. This standoff was interrupted by the arrival of a massive host of Goblins and Wargs from the Misty Mountains, forcing the divided factions to set aside their grievances to survive.
Significance
The conflict is a major event in the history of Middle-earth, serving as a precursor to the later struggles faced by the Fellowship of the Ring, including members such as Gandalf the Grey, Aragorn, and Gimli. The victory of the allied armies effectively broke the power of the Goblins in the North for many years. It also solidified the alliances that would eventually prove vital during the War of the Ring, when Frodo Baggins and his companions sought to destroy the One Ring.
