A Basque frontier duchy raised by the Franks along the Pyrenees (replacing the Roman-era Novempopulania), spanning the modern French Basque Country/Gascony and the Spanish Navarrese borderlands. Through the 8th century it swung between real independence under its own dukes and nominal Frankish/Carolingian overlordship, and its Basque fighters are traditionally credited with ambushing Charlemagne's rearguard at Roncevaux in 778.
Survived repeated Carolingian campaigns to subdue it; merged in personal union with the Duchy of Aquitaine by the 11th century, passed to Plantagenet/English rule in 1152, and was finally annexed to the Kingdom of France in 1453 (with its southern, Iberian portion evolving into the Kingdom of Navarre).
Polity-specific standard English-language history of the Basque peoples, covering the Duchy of Vasconia/Gascony directly; verified by title+author search on Open Library.