In the 8th–10th centuries. Europe was swept by a wave of violence. Muslims attacked from the west, Vikings from the north, Hungarians and Slavs from the east. In a frenzied whirlpool of raids, the states of Western Europe, which had not been subjected to such onslaught from the outside for over a century, had to adapt to new conditions, fighting on one front, negotiating, paying ransom on another, assimilating newcomer peoples and absorbing their experience. Feudal anarchy completed the destruction of the ancient foundations of society. But Europe survived this difficult test and emerged from it renewed. What did the Western European states lose in this long and disastrous war for them, what did they gain? What were the peoples who rushed like an avalanche towards Germany, France, and the Anglo-Saxon kingdom and why were they lucky? The famous French historian L. Musset devotes his book to these questions.