The Normans (Norman: Normaunds; ; ) were a population arising in the medieval Duchy of Normandy from the intermingling between Norse Viking settlers and indigenous West Franks and Gallo-Romans. The term is also used to denote emigrants from the duchy who conquered other territories such as England and Sicily. The Norse settlements in West Francia followed a series of raids on the French northern coast mainly from Denmark, although some also sailed from Norway and Sweden. These settlements were finally legitimized when Rollo, a Scandinavian Viking leader, agreed to swear fealty to King Charles III of West Francia following the siege of Chartres in 911. The intermingling in Normandy produced an ethnic and cultural "Norman" identity in the first half of the 10th century, an identity which continued to evolve over the centuries. The Norman dynasty had a major political, cultural and military impact on medieval Europe and the Near East. The Normans were historically famed for their martial spirit and eventually for their Catholic piety, becoming exponents of the Catholic orthodoxy of the Romance community. The original Norse settlers adopted the Gallo-Romance language of the Frankish land they settled, with their Old Norman dialect becoming known as Norman, Normaund or Norman French, an important literary language which is still spoken today in parts of mainland Normandy (Cotentinais and Cauchois dialects) and the nearby Channel Islands (Jèrriais and Guernésiais). The Duchy of Normandy, which arose from the Treaty of Saint-Clair-sur-Epte, was a great fief of medieval France. The Norman dukes exercised independent control of their holdings in Normandy, while at the same time being vassals owing fealty to the King of France, and under Richard I of Normandy (byname "Richard sans Peur" meaning "Richard the Fearless") the Duchy was forged into a cohesive and formidable principality in feudal tenure. By the end of his reign in 996, the descendants of the Norse settlers "had become not only Christians but in all essentials Frenchmen. They had adopted the French language, French legal ideas, and French social customs, and had practically merged with the Frankish or Gallic population among whom they lived". Between 1066 and 1204, as a result of the Norman conquest of England, most of the kings of England were also dukes of Normandy. In 1204, Philip II of France seized mainland Normandy by force of arms, having earlier declared the Duchy of Normandy to be forfeit to him. It