Rollo was a Viking who became the first ruler of Normandy, a region in northern France. He emerged as the outstanding warrior among the Norsemen who had secured a permanent foothold on Frankish soil in the valley of the lower Seine. After the Siege of Chartres in 911, Charles the Simple, the king of West Francia, gifted them lands between the mouth of the Seine and what is now Rouen in exchange for Rollo agreeing to end his brigandage, swearing allegiance to him, religious conversion and a pledge to defend the Seine's estuary from Viking raiders.
