when the islands had become Christianized, that accounts of the history of the islands were written from the point of view of the inhabitants in sagas and chronicles. The Vikings explored the northern islands and coasts of the North Atlantic, ventured south to North Africa, east to Kievan Rus (now – Ukraine, Belarus), Constantinople, and the Middle East. They raided and pillaged, traded, acted as mercenaries and settled colonies over a wide area. Early Vikings probably returned home after their raids. Later in their history, they began to settle in other lands. Vikings under Leif Erikson, heir to Erik the Red, reached North America and set up short-lived settlements in present-day L'Anse aux Meadows, Newfoundland, Canada. This expansion occurred during the Medieval Warm Period. Viking expansion into continental Europe was limited. Their realm was bordered by powerful tribes to the south. Early on, it was the Saxons who occupied Old Saxony, located in what is now Northern Germany. The Saxons were a fierce and powerful people and were often in conflict with the Vikings. To counter the Saxon aggression and solidify their own presence, the Danes constructed the huge defence fortification of Danevirke in and around Hedeby. The Vikings witnessed the violent subduing of the Saxons by Charlemagne, in the thirty-year Saxon Wars of 772–804. The Saxon defeat resulted in their forced christening and the absorption of Old Saxony into the Carolingian Empire. Fear of the Franks led the Vikings to further expand Danevirke, and the defence constructions remained in use throughout the Viking Age and even up until 1864. The south coast of the Baltic Sea was ruled by the Obotrites, a federation of Slavic tribes loyal to the Carolingians and later the Frankish empire. The Vikings—led by King Gudfred—destroyed the Obotrite city of Reric on the southern Baltic coast in 808 AD and transferred the merchants and traders to Hedeby. This secured Viking supremacy in the Baltic Sea, which continued throughout the Viking Age. Because of the expansion of the Vikings across Europe, a comparison of DNA and archeology undertaken by scientists at the University of Cambridge and University of Copenhagen suggested that the term "Viking" may have evolved to become "a job description, not a matter of heredity," at least in some Viking bands. Motives The motives driving the Viking expansion are a topic of much debate in Nordic history. The concept that Vikings may have originally