The Saxons were a confederation of Germanic tribes. The name Sak was used in antiquity to refer to the various tribes that inhabited the land northwest of what is today Germany between the Elbe and Ems rivers, including southern Jutland. Their modern-day descendants in Lower Saxony are considered ethnic Germans. Saxons took part in the Germanic settlement of Britain during and after the 5th century. Nobody exactly knows how many migrated from the continent to Britain. Estimates for the total number of Germanic settlers vary between 10,000–200,000. As fighters, the Saxons were ferocious, as people, they were hard working farmers and skilled craftmen.
Saxons, along with Angles, Jutes, Frisians and possibly Franks, invaded or migrated to the island of Britannia around the time of the collapse of the Roman Empire in the west. Saxon raiders had been harassing the eastern and southern shores of Britannia for centuries. To protect the towns from these Saxon assaults, the Romans had built a string of coastal forts called the litora Saxonica or Saxon Shore. But many Saxons and other folks had been permitted to settle in these areas as farmers long before the end of Roman rule in Britannia.
The Saxons resisted for a very long time to become Christians and be incorporated into the orbit of the Frankish kingdom. Finally they were decisively conquered by Charlemagne in a long series of annual fierce campaigns, which are known as the Saxon Wars (772–804). While Charlemagne campaigned in Hispania in 778, the Saxons advanced to Deutz on the Rhine and plundered along the river. With defeat came the enforced baptism and conversion of the Saxon leaders and their people. Their sacred tree, a symbol of Irminsul, was destroyed.
The Saxons were reduced to tributary status under Carolingian rule. There is evidence that the Saxons provided troops to their Carolingian overlords. The territory inhabited by the Saxons became a duchy, the Old Saxony. Later, the dukes of Saxony became kings like Henry I, the Fowler, 919, and later the first emperors, Henry’s son, Otto I, the Great of Germany during the 10th century, but they lost this position in 1024.
During the High Middle Ages, under the Salian emperors and, later, under the Teutonic Knights, German settlers moved east along the river Elbe into the area of a western Slavic tribe, the Sorbs. The Sorbs were gradually Germanized as they interbred with the Saxons inmigrants. Thus the name of Saxony later passed over to an entirely different region. This region subsequently acquired the name Saxony through political circumstances, though it was initially called the March of Meissen. The rulers of Meissen acquired control of the Duchy of Saxony in 1423 and eventually applied the name Saxony to the whole of their kingdom.

[...] of the Roman legions, the British Isles were invaded by three Germanic tribes; the Angles, Saxons, the Jutes, and Frisians. As they settled throughout England, various tribes combined for greater [...]