THE BATTLE OF AZANULBIZAR
Thrain does, however, still have his father’s Rolodex. He sends messengers north to the Gray Mountains, east to the Iron Hills, west to the Blue Mountains, out to the other six Dwarf-kings and their nations, telling them all about this horrible indignity suffered by Thror. It takes a couple of years, but eventually a huge host of Dwarves gathers in (and this is an odd coincidence) the region of Eotheod, where the Rohirrim were from originally and Gollum/Smeagol before them. This alliance of all the houses of the Dwarves starts at a known orc stronghold, Mount Gundabad at the northern tip of the Misty Mountains, and sacks it. Then they go south to the next orc stronghold, and they sack it, too. And they work their way south from the northern tip of the Misty Mountains to the southern tip, where they cross over past Isengard (no knowing what Saruman thought of all this) and then start going north up the other side, until finally they come back to the Western Gate of Moria, in the valley they called Azanulbizar, and that’s where they finally find Azog. Or at least, his gigantic army — Azog himself hangs back inside Moria.
Did I mention it’s snowing? It’s midwinter, in the middle of a blizzard, and the battle goes on for days and days and days. Gror (Thror’s brother who went to the Iron Hills) is dead by this point, but he has a son, Nain, who charges up to the open gate of Moria and taunts Azog to come out and play, which Azog does, and they fight for a long while until Azog slays Nain.
With Nain dead, Azog is all merry and cheery and shouting to his troops to rout these Dwarves, but then he looks around and realizes that while he was distracted fighting Nain, all the other Dwarves were killing every other orc, such that basically Azog was the last one alive. Azog shrieks and tries to flee back into Moria, but Nain’s son Dain (just a kid, by Dwarf standards) catches him and chops his head off.
So, victory for the Dwarves! Except for how they suffered like 50% losses, which is a lot of dead dwarves. Thrain, who lost an eye and the use of one leg in the battle, wants to press on into Moria, but he’s severely outvoted by the other six Dwarf-kings. They don’t have the personal stake in Moria that Thrain does, after all, and they just want to go home. Dain, too, thinks it’s a bad idea, because no way could they handle Durin’s Bane, the balrog, who’s still in there somewhere.
Afterwards Dain goes back to the Iron Hills, and Thorin takes what’s left of his retinue and goes to the Blue Mountains (which are west of the Shire), where they were poor and unhappy until the events of the Hobbit.
Some extra Battle of Azanulbizar facts!
1) After the battle the dwarves strip the gear from their fallen, so that orc scavengers can’t claim it, and chop down a forest’s worth of trees to burn their bodies; the smell of this fire is detectable as far as Lorien, on the other side of the mountains.
2) Tolkien notes that Dwarves don’t like funeral pyres, but they couldn’t build tombs enough for all the bodies, and that the Dwarves held these particular pyres sacred, and considered the “burned Dwarves” who fell in battle to be especially honored ancestors.
3) Thorin II claimed his epithet, Oakenshield, when his shield was broken during the battle; he picked up a tree branch with his free hand, and started beating orcs to death with it.
4) Azog’s son, Bolg, later led the goblin attack on Erebor at the Battle of Five Armies.