The withdrawal of troops in 410 had…
429 CE
The withdrawal of troops in 410 had marked the end of Roman Britain, for the central government never reestablished control, but for a generation there has been little other outward change.
Power has fallen gradually into the hands of tyrants, chief among whom is Vortigern, who, though the subject of many legends, may probably be safely regarded as an actual historical figure. (Unlike earlier usurpers, Vortigern makes no attempt to become Roman emperor but is content with power in Britain.)
Independence is producing separate interests in the island.
Christianity has made considerable headway by this date, but the leaders follow the heretical teaching of Pelagius, himself a Briton, who had emphasized the importance of the human will over divine grace in the achievement of salvation. (Some scholars maintain that the self-reliance shown in the maintenance of national independence is inspired by this philosophy.)
Yet, there is also a powerful Roman Catholic party anxious to reforge the links with Rome, in support of whom Germanus of Auxerre visits Britain in 429 at the behest of Pope Celestine, who has charged Germanus with the elimination of the Pelagianist heresy in Britain.
It may be partly to thwart the plans of this party that Vortigern makes the mistake of inviting Saxons to settle and garrison strategic areas of the east coast—in about 430; the date given by the Anglo-Saxon Benedictine scholar Bede (died 735) is between 446 and 454—though he certainly also has in mind the need to ward off seaborne raids by Picts, which at this time are troublesome.