Siege of Erebor

After Bard killed the Dragon Smaug, the Men of the Lake and the Wood-elves both laid siege to the Dwarves in the Lonely Mountain, the thirteen Dwarves of the Lonely Mountain under Thorin II Oakenshield having refused to share any of the treasure that they had recaptured from Smaug.
Thorin and Company were then trapped in a bloodless siege, with Thranduil and Bard hoping to wait them out. However, Thorin had sent messages of his plight to his relatives using talking messenger Ravens that lived on the Lonely Mountain. These reached Dáin II Ironfoot of the nearby Iron Hills, and he marched to the Lonely Mountain with 500 heavily armed Dwarves, most skilled veterans of the War of the Dwarves and Orcs.
The Orc army led by Azog attacked the Lonely Mountain and the conflict between the Dwarves, Men and Elves was quickly averted. In the Extended Edition, Dain sent forth his goat cavalry and spinning ballistas upon the Elven forces, who tried to counter with a shield wall and archer formations; during this early conflict, most of the Dwarven cavalry was killed or the Dwarves dismounted from their goats and elves were killed until the Were Worms burst forth from the earth and the fighting stopped instantly in the face of the new enemy.