Barbarian invasion of the 9th century.  Annals of Xanten (near modern Cologne), 845-853 and other chroniciles.   The Mid-Ninth century is often taken as the low point of Western European civilization. The Annals of the Abbey of Xanten, and other records express the situation.

845
Twice in the canton of Worms there was an earthquake; the first in the night following Palm Sunday, the second in the holy night of Christ's resurrection. In the same year the heathen broke in upon the Christians at many points, but more than twelve thousand of then were killed by the Frisians. Another party of invaders devastated Gaul; of these more than six hundred men perished. Yet owing to his indolence, Charles [the Bald, the rule of France] agreed to give them many thousands of pounds of gold and silver if they would leave Gaul, and this they did. Nevertheless the cloisters of the most of the saints were destroyed, and many of the Christians were lead away captive.

846
According to their custom the Northmen plundered eastern and western Frisia and burned down the town of Dordrecht, with two other villages, before the eyes of Lothair [The Emperor], who was then in the castle of Nimwegen, but could not punish the crime. The Northmen, with their boast filled with immense booty, including both men and goods, returned to their own country.

At this same time, as no one can mention or hear without great sadness, the mother of all the churches, the basilica of the apostle Peter, was taken and plundered by the Moors, or Saracens, who had already occupied the region of Beneventum. The Saracens, moreover, slaughtered all the Christians whom they found outside the walls of Rome, either within or without this church. They also carried men and women away prisoners. They tore down, among many others, the altar of the blessed Peter, and their crimes from day to day bring sorrow to Christians. Pope Sergius departed life this year.

847
After the death of Sergius no mention of the apostolic see has come in any way to our ears.

848
On the fourth of February, towards evening, it lightened and there was thunder heard. The heathen, as was their custom, inflicted injury on the Christians.

849
While King Louis [Ludwig, the King of Germany] was ill his army of Bavaria took its way against the Bohemians. Many of these were killed and the remainder withdrew, much humiliated, into their own country. The heathen from the North wrought havoc in Christendom as usual and grew greater in strength, but it is revolting to say more of this matter.

850
On January 1st of that season, in the octave of the Lord, towards evening, a great deal of thunder was heard and a mighty flash of lightening seen; and an overflow of water afflicted the human race during this winter. In the following summer an all to great heat of the sun burned the earth. Leo, pope of the apostolic see, an extraordinary man, built a fortification round the church of St. Peter. The Moors, however, devastated here and there the coast towns in Italy…

852
The steel of the heathen glistened; excessive heat; a famine followed. There was not enough fodder for the animals…..

853
A great famine in Saxony so that many were forced to live on horse meat.

883
The Northmen, ascending the Rhine, plundered and burnt many villages. Liutbert, archbishop of Mainz, with a small band of troops, attacked them and, after killing many of them, recovered much of the booty which they had taken. Cologne was rebuilt, except its churches and monasteries, and its walls with their gates and towers were restored.

885
The Northmen entered the territory about Liège, collected all kinds of provisions, and prepared to spend the winter there. But Liutbert, archbishop of Mainz, and count Heimrih, with others, fell upon them suddenly, killed many of them, and drove the others into a small stronghold. They then seized the provisions which the Northmen had collected. The Northmen, after enduring a long siege, during which they suffered from hunger, finally fled from the stronghold by night.

circa 950
Michael, bishop of Regensburg, after governing his diocese well for some years, gathered his troops and joined the other Bavarian nobles in resisting an invasion of the Hungarians. In the battle which followed, our troops were defeated. One of the bishop's ears was cut off, and after receiving many other wounds he was left for dead on the field. One of his personal enemies had fallen at his side, and, by feigning death when the Hungarians searched the battle-field, he escaped with his life. When he saw that he was alone with the bishop whom hated, he seized a lance and tried to kill him. But the bishop, having recovered consciousness, was able to defend himself, and, after a fierce struggle with his enemy, succeeded striking him down. After a long and perilous journey the bishop found his way back to Regensburg, greatly to the joy of his flock. All his clergy welcomed him as a bold warrior, his flock honored and cherished him as an excellent pastor, and his wounds and maiming redounded to his honor.