The Duchy of Burgundy is a state that exists in the Bella Gerant Alii timeline. After defeating the French in the Hundred Years War, The Burgundians divided French territory between themselves and the English. However, the declaration of Aquitanian independence and de facto Breton independence meant much of France's former territory was out of reach.
In 1490, the Second Breton War of Succession was waged between Brittany and Burgundy. The Breton faction was aided by Aquitanian and Austrian troops, as well as financial support from Hibernia. The Burgundians had English allies from Normandy, commanded by Prince Henry.
The three year war led to the decisive defeat of Duke John III and the Peace of Nantes, recognising Breton independence and the cessation of Burgundian claims to Brittany.