How did the ancient Saxons expand from northern Germany to Britain?

The ancient Saxons, who originally inhabited the region west of the lower Elbe River in what is now the German state of Lower Saxony, expanded to Britain primarily through maritime migration during the 5th century CE.12

While some Germanic foederati had settled in England as early as the 4th century, large-scale tribal migrations began around the middle of the 5th century. Historical tradition, notably recorded by The Venerable Bede, suggests that these groups were initially invited by a British king to serve as mercenaries to defend against the Picts and Scots. Following a revolt against their employers, these Germanic groups established settlements along the coasts and river valleys of southeastern England.31

Archaeological evidence indicates a complex process involving various tribal elements and contacts with Frisian and Frankish groups. Over time, these settlements evolved into the kingdoms of Essex, Sussex, and Wessex.34