After finally subduing the Saracen threat from the east, the eighth century brought to Europe a new invader--this time, unexpectedly from the north. These Scandinavians seemed but harmless savages conducting minor raids in the beginning, but they would soon wreak havoc throughout the Carolingian civilization. Although the main cause of their first attacks on western Europe are not known, from the start of the ninth century these Viking raids were already spreading so quickly that there was no immediate end in sight (by the mid-ninth century, it was estimated that the Viking Rorik had under his command 600 ships raiding on the Elbe river alone (Bradbury 21)).
Because, at first, the main objective of the Viking raids was mere plunder, the original targets of their melee were the easier targets of monasteries, trading outposts and any other lightly guarded target of movable wealth (Cambridge U 18-19). …
