Wales - (550-800)
Over the century following their setback at Mons Badonicus (see Post-Roman Wales), the Saxons - we may as well call them "English" now - pushed north and west to the Welsh hinterland. They attempted to establish control over the Wye valley, but in a decisive battle around the year 630 the Welsh of Gwent repulsed their advance and pushed them back beyond the River Wye.
This largely unheralded victory helped establish the independence of a "Welsh" Wales. Many "Welsh" heroes and bardic tales grew up from these battles with the Saxon English in the period 550-700 - although many of the battles took place far from the borders of modern Wales.
This point is easy to overlook; the history and culture of Wales was painted across a canvas that stretched across the whole of Britain. Welsh kings fought side by side with the Scottish Britons of the north against the English, in places as far afield as Lindisfarne in Northumbria.
Northumbria in ascendance
The English of Northumbria overcame the British tribes of Scotland through a series of campaigns and marriages, but Wales held out. It seems likely there were several English invasions of north Wales, perhaps reaching as far as Anglesey, in the years 600-700.
The Welsh even had some success outside modern Wales. Cadwallon achieved temporary success against the men of Northumbria around 633, but he was quickly killed the following year.
Mercia in ascendance
The kingdom of Mercia was the last of the major English kingdoms to come into being, and it was the one which posed the most immediate threat to the Welsh.
Mercia reached the height of its powers in the years 650-800, when it expanded to the Dee, Wye, and Severn rivers at the expense of the Welsh kingdom of Powys. The western borders of Mercia established to a large degree the eastern borders of Wales that we know today.
The Welsh were pushed back into the upland regions, and the fertile plains of the lowlands were lost to them. This loss of rich farming territory was not one the Welsh were likely to accept without a struggle, and struggle they most certainly did. They launched a series of raids attempting to regain the lowlands throughout the late 7th and early 8th centuries.
In an effort to better defend their new territory, Mercia erected an earthwork barrier, known as Wat's Dyke, extending from the Severn to the Dee estuary. This earthwork was probably constructed in the first quarter of the 8th century.