This is the period from about 409 AD to the start of Saxon political control, which was mainly in the late 7th century, though they are said to have captured the Bath area in 577 AD. Initially the Britons of Somerset seem to have continued much as under the Romans but without the imperial taxation and markets. There was then a period of civil war in Britain though it is not known how this affected Somerset. The Western Wandsdyke may have been constructed in this period but archaeological data shows that it was probably built during the 5th or 6th century. This area became the border between the Romano-British Celts and the West Saxons following the Battle of Deorham in 577 AD. The ditch is on the north side, so presumably it was used by the Celts as a defence against Saxons encroaching from the upper Thames Valley. According to the Anglo-Saxon Chronicle, the Saxon Cenwalh achieved a breakthrough against the British Celtic tribes, with victories at Bradford-on-Avon (in the "Avon Gap" in the Wansdyke) in 652 AD, and further south at the Battle of Peonnum (at Penselwood) in 658 AD, followed by an advance west through the Polden Hills to the River Parrett.