The Duchy of Aquitaine was originally chartered as English lands at the end of the Hundred Years War. However, the Count of Bearn, father-in-law of a young daughter of Charles VII of France, gathered troops and support of the local nobility and declared an independent nation in the name of his unborn grandson, throwing back Burgundian armies at Toulouse and Limoges
Aquitaine, under Francis II, gave military support to Brittany during the Second Breton War of Succession, concerning the marriage of the Breton heiress Anna and Maximilian I of Austria. Although victorious in the war, the Aquitanians lost their Duke, leading to the crowning of Francis III and rule under his mother - regent Marie of Angouleme.
In 1623, Navarre declared its independence. The nobility of Navarre wished to elect one of their own but the Aquitanian duke - Geoffrey III went to war with them and forced an election on the people, who chose a younger cousin of Geoffrey as their new king. A law was passed by the Navarrese nobility to ensure their independence, forbidding the Foix dynasty to rule both nations under one monarch.
By the year 1817, the Duchy of Aquitaine was formally dissolved and split into several minor states. The Foix dynasty still maintained control over Bordeaux, Brittany, Aquitaine, Navarre and Anjou, in a personal union lasting until 1982, when the Foix dynasty was exiled and the French Republic was proclaimed.
In 2017, the French Republic and sub-kingdoms collapsed and a new France was created under the House of Bourbonnais. The ruling dynasty retained absolute power in many of the western provinces whereas the eastern regions; such as Picardy and Lorraine retained autonomy. The Bourbonnais family fell from power after attempting to annex Franche-Comte. The intervention of Castille and Hibernia ensured the fall of the French Union.
After the loss of independence, the territory of Aquitaine was split between Navarre (the lower regions) and Loire (the upper regions).