Battle of Five Armies

The Battle of the Five Armies is an event in The Hobbit trilogy and mentioned indirectly in The Fellowship of the Ring.

Prelude
Prior to the battle, Thorin Oakenshield went on a quest to reclaim the lost kingdom of Erebor (AKA the Lonely Mountain) after it was stolen by Smaug. He and his company were smuggled into Lake-town by Bard the bowman before they are discovered by the Master of Lake-town's guards and taken to the master himself. Thorin promised to give the people of Lake-town a share of the treasure to help them rebuilt the kingdom of Dale and rebuild Esgorath ten times its original size.

Aftermath
Many other people came out unscathed, but several characters were killed in the Battle of the Five Armies. Bilbo Baggins laid next to Thorin Oakenshield, who called the hobbit his friend and apologized how much danger he put Bilbo through. Despite Bilbo's efforts to keep Thorin alive, the Dwarf king succumbs to his wounds. Bilbo cried over his deceased friend's body. The hobbit left Erebor and settled back down in the Shire and raised his nephew, Frodo Baggins. Later, the battle also indirectly caused the War of the Ring.

Trivia

 * This is considered the first conflict in the War of the Ring by fans.