Some background information for my sci-fi YA series Terminus…
The great Imperial War occurred three centuries before Terminus begins. It led to the creation of the Great Alliance and the super-human Royals. When the war was over, the political map of the Shoreless Sea had forever changed. The Great Alliance comprised what remained of the Somontran Republic in the middle, with half of the Commonwealth to the west and the Sovereignty to the east. They had defeated the Empire and the Prophets, but existential threats remained. The Baraki went from a minor irritant to a major interstellar power threatening the ragged remains of the Commonwealth and the new Great Alliance. Even worse, the Ronain Empire now sat on the border of the GA promising annihilation.
The Ronains fought a bloody war with the nascent Great Alliance all the way to Parid itself. The GA beat them back only through the strength of their Royals and the sacrifice of Savior Katherine Cayale herself. The war ended without a surrender or a formal ceasefire. The Ronain Emperor promised to bury the GA and erase it from history. Both sides prepared for the next inevitable confrontation.
The Second War occurred twenty years later. The GA learned the second generation of Royals were not as strong as the first and each generation would become progressively weaker. The Royals would not be able to storm Ronain battleships single-handedly anymore. Advancing GA technology could not close the gap with the enemy. Time was against them. Majestrix Virginia Cayale, the first Daughter of Savior, decided to preemptively attack while they still possessed an advantage. The bloody invasion ended in another stalemate without any resolution.
For the next three centuries, the Ronains randomly attacked GA worlds on the border. They would massacre a large section then simply withdraw. Millions died and an entire society of the former Sovereignty worlds grew up hating the Ronains. The Baraki also regularly attacked the GA as each generation of their people required honorable combat. The GA struggled to defend its borders on both sides from alien invasion.