Dwarf-kingdom

A name that could in principle apply to any of the kingdoms of the Dwarves, but in practice was used to describe Erebor, the realm of the Kings under the Mountain. This was a kingdom with a long and troubled past, originally founded by Thráin I in III 1999, but abandoned by his successor Thorin I, who moved the royal seat into the Grey Mountains. After Thorin's departure, there was no Dwarf-kingdom under the Lonely Mountain for nearly four hundred years, until King Thrór returned there to rule. In his time the prosperity of Erebor became legendary, and its riches attracted the attention of the Dragon Smaug, who sacked the kingdom and drove out the few surviving Dwarves.

Smaug remained in the halls of the Dwarf-kings beneath the Lonely Mountain for more than one hundred and seventy years, until Thrór's grandson Thorin Oakenshield led a small company of Dwarves (and a certain famous Hobbit) back to the Lonely Mountain. Against all reasonable hope, the Dragon was defeated and the Dwarf-kingdom re-established, though Thorin was slain in the Battle of Five Armies before he could take up the Kingship. The title therefore fell on his heir Dáin Ironfoot, who founded the Kingdom of Dáin that would survive into the Fourth Age.