Castles

"As the Dark Ages waned, the popularity of castles increased. In fact, one could say that the rise of the castle marked the transition period between the Dark Ages and the High Middle Ages, as empires and kingdoms collapsed under the onslaught of new invasions and migrations, like the Roman Empire. The Vikings shattered the feeble Celtic and Anglo-Saxon kingdoms of the British Isles, threatening the remnants of the old Frankish empire in the west. The Norsemen, mainly those from modern-day Sweden, also tangled with the Slavs of Eastern Europe, leading to the creation of the Russian kingdoms. In the south and west, the forces of Islam swept into Europe, destroying the armies of weak Christian kingdoms while Byzantium fended them off in the East from the 7th century until the 9th century of the Early Middle Ages.  

Throughout the Dark Ages, the kingdoms that successfully resisted the onslaught of the "barbarians" from the North and East and the Islamic forces from the South relied heavily on fortifications for their defense. Both Viking and Moor also adopted fortified positions to strengthen their hold on the territories they occupied and to enhance their offensive operations. In the 9th century, Alfred the Great led Saxon forces against the Norse intruders, laying down the foundations of a new nation that would come to be known as England. By the time the Germanic ruler of the Latin regions of the Frankish empire in the West was succeeded by the first dynasty of Latin kings in the 10th century, the Viking problem was well in hand. Rollo's Norsemen settled in Normandy and his heirs became vassals to the Frankish king early in the 9th century. Both Hugh Capet, who founded the Latin dynasty of France, and his son who succeeded him, had to contend with their vassals more than any external enemy. The castle played an important role in their struggles to maintain their power over their dominions." ^[1]

1. Kaufmann, J.E.; Kaufman, H.W. The Medieval Fortress: Castles, Forts, and Walled Cities of the Middle Ages. Da Capo Press: Cambridge. 2001.