General history

During the 9th century they expanded beyond these three bases, arriving first as rapacious raiders (looting monasteries and capturing slaves to sell in the Middle East) but soon establishing themselves on a more permanent basis.
Swedes called Rus or Varangians established fortified cities at Novgorod and then at Kiev, creating the first Russian state, and traded down the great rivers of Russia to Byzantium and Persia. Norwegian Vikings established kingdoms in Ireland, where they founded Dublin about 840, and in northwestern England.
They settled Iceland and colonized Greenland in the 10th century and founded the short-lived North American colony called Vinland in the early 11th century. Great armies of Danes and Norwegians conquered the area called the Danelaw in England, overthrowing all the Anglo-Saxon kingdoms except King Alfred's Wessex. They attacked cities in France, Germany, the Low Countries, and Spain and, in 911, seized control of Normandy in France, where their descendants became known as the Normans.

After conquering and settling in foreign lands, the Vikings came under the cultural influence of the conquered peoples. Originally pagan worshipers of Thor and Odin, many became Christians, and during the 10th century they brought Christianity to Scandinavia.
The process of conquest slackened during the 10th century as civil wars raged in Scandinavia. Out of these wars powerful new kingdoms emerged with great new fortresses, including Trelleborg in Denmark. Soon armies of a renewed Viking age were on the move. In 1013, Sweyn of Denmark conquered all of England. His son, Canute, built an empire that included England, Denmark, and Norway.
By the second half of the 11th century, however, the coming of stronger political systems and stronger armies in Europe, the development of new types of ships, and the redirection of military endeavor by the Crusades brought the Viking Age to an end.