Charles the Simple

Son of Louis the Stammerer, born posthumously, marginalized for years before claiming the West Frankish throne. His Treaty of Saint-Clair-sur-Epte in 911 ceded the lower Seine valley to the Viking warlord Rollo in exchange for baptism and homage — the founding act of the Duchy of Normandy. Deposed by Robertian rivals in 922 and held captive until his death.