Battle of Azanulbizar
The Battle of Azanulbizar (Third Age 2799) was the penultimate battle in the War of the Dwarves and Orcs. It was fought beneath the East-gate of Moria in the valley of Azanulbizar, called Nanduhirion in Sindarin or Dimrill Dale in Westron. Therefore the event is also known as the Battle of Nanduhirion and the Battle of Dimrill Dale.
Prior to the Battle
The War of the Dwarves and Orcs was started when Azog the Orc-chieftain of Moria captured and mutilated Thrór, King of Durin's folk. Azog carved his own name in runes onto Thrór's severed head, and then let his companion Nár escape so that all Dwarves would know that an Orc now ruled Moria. Full of righteous fury, Thrór's son Thráin II gathered a great army of Dwarves, including those not of Durin's folk (Firebeards and Broadbeams from the Blue Mountains and those from the far East of Middle-earth). For six years they systematically destroyed the Orc-holds of the Misty Mountains, until only Moria was left where those Goblins that survived the destruction fled.
The exact number for the Dwarves was not specified, but it can be estimated at being somewhere between six to ten thousand Longbeards, Firebeards, Broadbeams, Ironfists, Stonefoots, Blacklocks, and Stiffbeards. The Orcs, as stated above, came from Moria, and from as far north of the Misty Mountains as Mount Gundabad. So their numbers can be estimated at fifteen to twenty thousand Orcs.
The battle started on a dark day of cold winter with no sun. The Dwarves had marched into the Dimrill Dale where they found the great East-gate and sent up a great noise. They soon discovered that on the western slopes above thousands of Orcs had gathered and more were coming out of the East-gate, outnumbering them and holding the higher ground.
The first Vanguard led by King Thraín, assaulted the slopes but were driven back with loss, into a wood near the Mirrormere, where Frerin youngest son of Thraín was slain along with Fundin, father of Balin, along with many others. Thraín himself was wounded, as well as his eldest son Thorin II Oakenshield. Who's shield was broken during the battle and had to use an oak branch that he hewed off a tree to defend himself.
Elsewhere, the battle swayed to and fro until Náin from the Iron Hills, arrived with a host of fresh troops with him. Naín, and his Dwarves hewed through the Orc lines with their mattocks shouting AZOG! AZOG! AZOG! until they got to the very steps of the gate, in-which Naín called upon Azog to come out and fight. When Azog emerged from the inner gate with his guards, Naín was very tired and half blind with rage and tried to swing as hard as he could at Azog but the orc darted aside, and he missed, which splintered his mattocks on the ground. The orc kicked him in the leg when he dodged the Dwarf's blow, making him stumble, at which Azog tried to decapitate him but Azog only broke Naín's neck because of the strong mail he was wearing, Naín died instantly. Azog laughed at this, but when he looked out into the valley he found that his entire army was routed. Those that could were fleeing southwards, and all his guards were killed as well. With that he fled back to the gate. But Náin's son, Dáin, leaped up the steps after him with his red axe and just before the gate he hewed off Azog's head, thus ending the war. He was just 32-years old at the time, very young for a Dwarf, and it was remarked an amazing feat. Dáin would later become King under the Mountain as Dáin II Ironfoot.
The Dwarves were victorious, but with a heavy casualties. Half of their forces dead or mortally wounded. But the Orcs casualties were ten thousand. After the battle, King Thráin wanted to enter and reclaim Moria, the ancestral home of Durin's folk. However, since the Dwarves had taken heavy losses and the Dwarves of the other Houses did not see any benefit in it for them unless they got some treasure from Moria. More significantly, Dáin had peered beyond the East-gate after slaying Azog, and saw that Durin's Bane still lingered within and advised Thráin not to enter. They then stripped the dead, so the orcs couldn't plunder them, and felled all the trees in the valley which they made many pyres with, and put there dead on them to burn. For they could not bury them all in fashioned tombs of stone, as was their custom for it would take many years. So those that fell in that battle were known proudly as Burned Dwarves. The Houses then parted ways, returning to their homes to the North, East, and West.
Thráin, with what was left of Durin's folks' forces, went back to Dunland, and shortly afterwards wandered in Eriador till they settled in the Northern Blue Mountains. There Durin's folk regrew slowly in population and waited till the days they could take back the halls of Erebor, and Khazad-dum.
Although the Dwarves suffered heavy casualties, the battle would have lasting repercussions for the Orcs of the Misty Mountains. Their numbers had been severally shrunk after the battle and never fully recovered. If it hadn't been for the battle the Bilbo Baggins and his thirteen Dwarf companions may have never made it to Erebor. The Battle of Five Armies wouldn't have been won buy the army of Elves, Men, and Dwarves. And The Fellowship may have never got through Moria alive.