War of the Dwarves and Orcs
The War of the Dwarves and Orcs was a great war fought between the two races.
From 2790 to 2793 the Longbeards that were Durin's folk responded to this tragedy by gathering their forces, and calling on all the other Houses of the Dwarves but it took them three years to fully gather their strength. In 2793 they attacked, assailing sacking one by one all the Orc-holds they could from Mount Gundabad in the north, to the Gladden Fields in the south.
Most of the war was fought underground, in the great mines and tunnels of the Misty Mountains, where Dwarves excel in combat. The war climaxed in 2799, when the final battle was fought in the valley outside the eastern gates of Moria, the Battle of Nanduhirion. The Dwarves finally won this notoriously bloody encounter when reinforcements arrived late on the scene from the Iron Hills.
After the battle, Thráin II son of Thrór wanted to enter Moria and reclaim it, but the Dwarves not of Durin's folk refused, saying that the city was not their Fathers' House, and they had honoured Thrór's memory by fighting, and this was enough. Dáin II Ironfoot also warned Thráin that Durin's Bane still dwelt within Khazad-dûm, and that forces beyond the Dwarves would have to defeat it bfore they could reenter the city.
The war was very costly for the Dwarves. Half of those involved in Nanduhirion were killed and possibly a couple thousand more were killed throughout the rest of the war. Náin son of Grór, Frerin second son of Thráin II, and Fundin son of Farin, the father of Balin were among the more noted casualties. Thráin II himself lost an eye, and Thorin was wounded when his shield broke and he had to use an oak branch to defend himself. This probably led to his later name Thorin Oakenshield.
Other effects of the war were that the Orcs of the Misty Mountains virtually disappeared as a threat for Eriador and Wilderland. 150 years later the Orcs of the North were beginning to recover, but their population was further reduced during the Battle of Five Armies in 2941, where Bolg son of Azog tried to avenge his father, and in the process destroying three fourths of the Orcs of the Misty Mountains.
It is probable that without this War and the final slaughter of the Battle of Nanduhirion, the later War of the Ring would have been lost in the north, and the Ring-bearer might never have made it south to Mordor.