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 insult by gathering their forces, calling on all the other houses of the Dwarves. In 2793 they attacked, sacking one by one all the Orc-holds of the Misty Mountains from Mount Gundabad in the north to the peak of Methedras 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, and as such they went unaided by the other Free Peoples. The war climaxed in 2799, when a 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 they had honoured Durin's memory by fighting, and this was enough. Durin's folk on their own could not muster a force strong enough to enter Khazad-dûm. Probably the Dwarves also feared Durin's Bane was still present.
The war was very costly for the Dwarf race, as nearly half of those involved were killed. 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: the goblins of the High Pass near Rivendell were some of the few survivors.
150 years later the Orcs of the North still had not fully recovered, but their population was further reduced during the Battle of Five Armies in 2941, where Bolg son of Azog tried to avenge his father.
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.