The Atlantic Dominion is an amalgamation of seventeen small nations and city-states that lost their independence following the Commonwealth War.
Unlike the city-states of the Ohio valley, who joined into a Confederacy due to pressure from Quebec and the Mississippi Empire, the city-states along the Atlantic coastline had little to no reason to join in any sort of overall organization. The closest that existed was the Chesapeake Federation, which was a very loose defensive treaty between seven members.Borders between the states changed constantly, some as little as ten years before the Commonwealth War.
During the war, the states provided light warships, sailors to crew ships built in other nations, and regiments of troops to fight in the northeast. Tough and reliable, these units also gained some notoriety after some massacres and pillaging.
This particularly irked Field Marshal Bjorn Solheim, commander of the Imperial Central Army Group. When the Mississippi Empire turned and the line collapse, Solheim marched his army group down the seaboard. He refused to let any of the seventeen nations surrender, instead conquering every single one.
Instead of partitioning the seventeen nations and allowing their annexation by neighboring successor kingdoms, the Imperial Commonwealth assembled the seventeen nations into the Atlantic Dominion, an occupied territory. Field Marshal Solheim was named the Military Proconsul of the territory, and rules it with an iron fist.
Under the yoke of the Imperial Commonwealth, the people and cultures of Atlantic America are severely repressed. The vast majority of people live at a level just above slavery. Many men are conscripted into the Commonwealth’s ranks, and their production is sold under the Commonwealth’s banner.
The higher society, such as survived the war, has survived by changing itself into an autocratic caste. It is an open secret that the Commonwealth will someday grant the Dominion independence, and part of that will involve selecting a monarch and assigning titles. They work to further the Commonwealth’s goals in the hopes of gaining power when independence comes to them.