Three main groups – Magyars, Saracens and Vikings – launched raids on Europe in the 9th and 10th centuries, as well as being involved in trade. It was the Vikings who proved the most adaptable colonists. Settlements established by them in the north Atlantic and North Sea, Russia and the Mediterranean developed into strong independent states.
The relatively effective rule of the Carolingians in western Europe and of the various kings in Britain gave some assurance of security from attacks both to religious communities and merchants. By the 8th century abbeys and markets were not fortified and the masonry from Roman defences was often used for other building work. The wealth accumulated in such places offered tempting bait to external raiders. They came from countries whose rulers and people were also often partners in trade, the objects of missionary activity and political overtures or attempts at control, and who interacted with the politics of the countries their countrymen raided by entering into political agreements with them or acting as mercenaries. In the 9th and 10th centuries western Europe suffered attacks in particular from bands of Saracens, Magyars and Vikings.
After the Muslim occupation of Sicily, begun in 827 (though conquest was not complete until 902), Saracen pirates, possibly mainly from Crete and the eastern Mediterranean, established temporary bases such as Bari and Taranto on the coast of southern Italy, and later in southern Gaul, from which they were able to attack centres in the western Mediterranean until ousted by Byzantine armies in the late 9th century. Corsica and Sardinia were frequently attacked and many monasteries and towns in central and southern Italy (including Rome itself) were pillaged.
The nomadic Magyars, who may have moved into the Hungarian Plain from the east in the last years of the 9th century, plundered the neighbouring areas: northern Italy, Germany and even France. Their skill as horsemen and their advantages of speed and surprise made opposition difficult. They also acted as mercenaries against the Moravians and the Bulgars. Major defeats were inflicted on east Frankish armies between 899 and 910, but thereafter the German rulers achieved important successes, culminating in the defeat of the Magyars at the Lechfeld in 955.
In the east, the threat of Magyar raids was halted by a joint enterprise by the ruler of Kiev and the Byzantine emperor. A Magyar embassy to the German emperor Otto I in 973 marked the beginning of a more settled way of life for the Magyars. Missionary activities thereafter from Regensburg and Passau resulted in Stephen (977 – 1038), the first Christian king of Hungary, being given the right to set up the Hungarian church with its own bishoprics.
Frankish expansion into Frisia and Saxony in the 8th century may have prompted defensive aggression on the part of the Danes. Franks and Danes were able to conclude various agreements in the first half of the 9th century, including the conversion to Christianity of a number of leading Danes and the settlement of Viking groups at strategic points to defend outlaying regions of the Carolingian empire. However, raids on Lindisfarne in 795 and on the important trading emporium of Dorestad in 834 were the beginning of a grim record of attacks on both France and England until the end of the 9th century.
Although the raids were no doubt described in exaggerated terms by survivors, they undoubtedly caused much misery and distress; for example the bishop of Nantes and all his clergy were murdered in 842. Increasingly effective defence (including buying time with tribute payments and the building of new fortifications) against the raids was mounted by the Frankish and English rulers. The practice of ceding the Vikings territory in order to act as a buffer culminated in the granting of the county of Rouen in 1911 to Rollo, which with hindsight can be recognized as the foundation of Normandy.
The Vikings were highly adaptable colonists as well as traders and raiders and their shipbuilding and seafaring prowess enabled them to journey far afield. The Danes settled in England as well as France. The Norse ventured to Ireland, Man, Scotland, the Orkneys, the Faroes, Iceland, Greenland and even as far as Newfoundland. The Swedes travelled down the great rivers of Russia and founded the kingdom of the Rus based at Kiev and Novgorod where they formed links with Byzantium.