Q&A: How did the Normans learn to build castles?

The Normans, as is widely appreciated, were originally Norsemen: Vikings who settled in the area around the Seine estuary in the late ninth and early 10th centuries. The traditional date for the founding of Normandy is AD 911, when the authority of the Norman leader, Rollo, was recognised by the king of France. Castles appeared somewhat later, with the earliest examples being constructed around the turn of the first millennium. They differed from earlier fortifications by being smaller and taller: the distinctive feature of early castle design wasthe distinctive feature of early castle design was the great artificial mound of earth, or motte. Dating a mound of earth is difficult, since it relies on the discovery of datable ‘small finds’, and so establishing a precise chronology for mottes is impossible. Nor is it possible to say for certain how and why the design originated, other than to observe that the rise of castles seems to coincide with an intensification of lordship across northern France in the decades around the millennium. Evidently someone had the notion of building a great mound of earth to assert his power and the idea caught on fast.