Some Saxons, along with Angles, Jutes and Frisians, invaded Britain in the early Middle Ages, giving their names to the kingdoms of Essex, Sussex and Wessex (the lands respectively of the East, South and West Saxons), which with the shorter-lived Middlesex eventually became part of the kingdom of England.
A majority of the Saxons remained in continental Europe, forming from the 8th century the Duchy of Saxony. They long avoided becoming Christians and being incorporated into the orbit of the Frankish kingdom, but were decisively conquered by Charlemagne in a long series of annual campaigns (772 - 804). With defeat came the enforced baptism and conversion of the Saxon leaders and their people. Even their sacred tree, Irminsul, was destroyed.
Under Carolingian rule, the Saxons were reduced to a tributary status. There is evidence that the Saxons, as well as Slavic tributaries like the Abodrites and the Wends, often provided troops to their Carolingian overlords. The dukes of Saxony became kings (Henry I, the Fowler, 919) and later the first Emperors (Henry's son, Otto I, the Great) of Germany during the 10th century, but lost this Position in 1024. The duchy was divided up in 1180 when Duke Henry the Lion, Emperor Otto's grandson, refused to follow Emperor Frederick Barbarossa into war in Italy.
The later Upper Saxony in the southern part of eastern Germany, from 1806 to 1918 the kingdom of Saxony, and from then till 1952, and again from 1990 until today the Free State of Saxony, became so known through the acquisition of the dukedom of Saxony by the Margrave of Meissen in 1423. His successors' territory, in fact, lay beyond the traditional lands of the Saxon people.
The label "Saxons" was generally applied to German settlers who migrated during the 13th century to south-eastern Transylvania in present-day Romania, where their descendants numbered a quarter of a million in the early decades of the 20th century. Most have left since World War II, many of them during the 1970s and 1980s due to the Romanianisation policies of the Ceauşescu regime.
Since reunification in 1990, three federal states of Germany derive their name from the Saxons: Niedersachsen or Lower Saxony, whose area corresponds roughly to the traditional Saxon lands between the Netherlands and the Elbe River; Sachsen-Anhalt, located around the city of Magdeburg; and the Free State of Sachsen or Saxony, which included the city of Dresden, in eastern Germany bordering the Czech Republic, the old kingdom (see above).