The Normans were born from collision. In the early 10th century, Norse Viking bands had been raiding the coasts and rivers of West Francia for decades. Instead of trying to expel them, the Frankish crown chose a gamble. In 911, the Viking leader Rollo swore loyalty to Charles III in exchange for land along the lower Seine. This agreement—known as the Treaty of Saint-Clair-sur-Epte—created the Duchy of Normandy. What followed was one of the most successful cultural transformations in medieval his