Lore:War of Succession
After King Borgas of Skyrim was killed by the Wild Hunt in 1E 369, a civil war was sparked. Imperial scholars blamed the arbiters of the succession, the Moot, for not choosing Jarl Hanse of Winterhold, who they considered the obvious choice.
The Skyrim Conquests had started in 1E 240, and saw Skyrim gaining control of most of High Rock and Morrowind, as well as some territories in Cyrodiil's Nibenay valley aiding in the Alessian Slave Revolt that birthed the Alessian Alley, leading the two empires to become close allies. However the Fundamentalist Alessian Order came to prominence in the Alessian Empire, and while controversial within Skyrim enjoyed much influence there. The Alessian Order was anti-elven in nature, seeing the expulsion of the remaining Ayleids in Cyrodiil, most of whom fled to Valenwood and High-Rock integrating into the elven populations in those provinces. High King Borgas was an ally of the Alessian Order, and wanted to discuss a joint-invasion of Valenwood with the Alessians. In response the Wood Elves used the Green Pact to call a Wild Hunt, resulting in High King Borgas' death. His death marks the end of Ysgrammor's line, and the loss of the Jagged Crown. While it was assumed that his body was lost, it was secretly returned to Skyrim and buried in Korvanjund.
The war was disastrous for Skyrim; it lost its possessions in the provinces of High Rock, Morrowind and Cyrodiil, and cities such as Windhelm were sacked. The territories in Morrowind were lost thanks to the formation of the First Council, an alliance of the Chimer and Dwarves who had previously feuded over religion and territory since the Chimer first entered the province, and after expelling the Nords it was agreed the two races would jointly rule over Morrowind thanks to the personal friendship of Indoril Nerevar and Dumac Dwarfking, renaming the province to Resdayn. Though in response many dwarven clans chose self-exile moving west into Hammerfell.
In 1E 420, the Pact of Chieftains brought an end to the conflict, and Olaf One-Eye was named High King after he had managed to subdue the Dragon Numinex and imprison him within Dragonsreach in Whiterun.