Brythonic Kingdoms, Saxon & Dane invasion, Vikings (400s- 1000s)

Migration of Northern Europeans to the British Isles during the first millennium, post-Roman Empire. Anglo-Saxons, Danes, and Vikings (Wikipedia links used).

Wales, first called Cambria, and Great Britain, known as Albion. The countries were once divided into many so-called petty Kingdoms. For example, Rhos and Edeirnion were before the merging of Gwynedd with other Kingdoms during the 5th century AD. During this period, the Saxon territories in England were first established during the settlement of the Anglo-Saxons. They were a religiously Pagan group of tribes from the European North Sea who had invaded the British Isles following the departure of the Roman legions after four centuries of controlling the Brittonic people and mining their lands. This was an era when the borders of Wales were once much more than they are today. The territories were further east and north than now within what is today England. The Celts were called the Brythons (today Britons), and they were Celtic-speaking people who had permanently inhabited their own territorial lands for more than a millennium after living in hillfort enclosures and roundhouses from the end of the Bronze Age in Britain. 

Image courtesy of Wiki Commons, attributed to mbartelsm, Anglo-Saxon homelands & settlements, c, 450 AD.

The British Isles saw an insurgent invasion from Germania in the Southwestern Baltic Sea after the turn of the 5th century. That was after the withdrawal of Roman troops from the British Isles. However, migration to and from Celtic Britain was not uncommon for the Gauls as fellow Celtic tribes, and they were already migrating northward from the Frankish empire over the English Channel. They had done so during the Roman period because the similarity in Celtic languages made it easy for them to assimilate. The era was called the Germanic Iron Age. During the years 550- 880 AD (in Scandinavia). 

The origins of the Germanic tribes are that they had come from east of the River Rhine. The river splits the modern-day countries, Netherlands, France, Germany, and Switzerland to the north and east of the Alps Mountain Range. Firstly, when the Roman Empire conquered most of Western Europe, they divided their territory to the east and the west of the Rhine. This left the tribes to the east of the river since then were independent of Roman rule. The separation was due to their overambitious land grab and the unforeseen circumstances involving their defeat at the Battle of the Teutoburg Forest (9 AD) by Arminius and the Barbarians. The Celtic Britons had more in common with their fellow tribals from the Germanic regions than Romans from Atlantic Europe and Southern Europe. 

The first wave of migration of boat-voyaging Germanic-speaking tribes came in the 5th century from the North Sea of Europe. The tribes included the Germanic Saxons and the Frisians (also from the Netherlands). They were from modern-day Germany. Also from southern Scandinavia (today) were the Angles and Jutes. They were part of the Danes tribes of modern-day Denmark. And then later emerged the Vikings during the 9th century from northern Scandinavia, the Norwegians and Swedish. The different groups of tribes were in many cases similar to seafaring pirates today. 

The first 5th-century Brythnoic invasions actually began between Celtic tribes in the north of Britain. The Picts successively invaded England after the retreat of the Roman legions who had previously subdued the war-like Scottish Celtic tribe. The King of Britain, Vortigern, had asked for the help of Saxon mercenaries to protect the Brythnoic people. He enlisted the 2 Saxon-based siblings, Hengist and Horsa, who would defend the Brythonic Kingdoms from the Picts who ventured south of the northern divide of Haidrian's wall. However, the Saxon brothers changed allegiances and invaded Britain from the south with their fellow Saxons and with help from the Jutes. After their successful invasion, Hengist became the first British Anglo-Saxon King of the Kingdom of Kent as part of the future Heptarchy in southeastern England, the nearest point between Great Britain and the European continent. However, one famous historical figure from the 400s is King Arthur. What he did was to successfully prolong the invasions through successful warfare defending Britain (mentioned by Nennius).

Image courtesy of Wiki Commons, attributed to Evil Berry, Hengist, and Horsa arriving in Britain.

One of the most famous Anglo-Saxons was Raedwal of East Anglia, who lived in the early 7th century. Rædwald's funeral was a perfect example of a Saxon King's burial, c. 620. Almost a century prior, his burial mound was discovered in a field in Suffolk, England. A treasure hoard and a ship were found. The find included the famous Sutton Hoo helmet. The mask was later reconstructed in the 20th century to show the intricate metalwork undertaken to construct such a fearsome helmet used to go into battle.

Image courtesy of Wiki Commons, attributed to Gernot Keller, The Saxon Sutton Hoo helmet burial.

Apart from the eastern-reaching Kingdoms of the North Sea in England, the Anglo-Saxons never directly conquered further than the England-Wales border in the Welsh Marches. What they did do was stabilize English Kingdoms to rule through marriage. On the Welsh border was the Kingdom of Mercia, which used the Saxons' help to expand their ambitious territorial reach. The Mercians had constructed a land border named Offa's Dyke. The Dyke's construction was during the mid to late 8th century. The naturally built defensive mud dyked wall was between the Welsh Kingdom of Powys and English Mercia and was designed by and named after King Offa. The dyke was a territorial border that is recognized today as the official land border of Wales. Mercia had officially subjugated the Kingdoms of Powys and Gwynedd to the North of Wales. The Mercians used Anglo-Saxon mercenaries in battle. This tactic made them a formidable force to reckon with. The Welsh would be their royal subjects for centuries to come, that's until the emergence and resistance of Gwynedd's cadet branch, the Royal House of Aberffraw, 9th century.

After the 7th century, petty kingdoms had come and gone and were incorporated into bigger Kingdoms. Morgannwg, or Seisyllwg, Wales are examples. The Anglo-Saxon subversion of England and Wales was finally complete. However, a different foe emerged in the form of Vikings from Scandinavia in the 9th century. By then, the British Isles had been successively conquered in part by Saxons, Danes, and Vikings directly after the Romans and the Normans were yet to come. The Scandinavian and Germanic tribes in the British Isles had coordinated in establishing the Viking Uí Ímair dynasty as monarchs in some of the Kingdoms in Ireland; Dublin, Leinster, Limerick, Waterford, the Mann, and the Isles, as the areas of Northern England (Northumbria) and Scotland, and their ancestral homeland of Norway. The union created an ability to travel by boat from Western Ireland on the Atlantic Ocean to the Baltic Sea, specifically Norway, and a distance of over 1400 km. The leaders of their respective Kingdoms would have been able to muster troops hired as Saxons or Viking mercenaries to invade Kingdoms throughout the British Isles, which they did successfully. This became a common theme involving Kings and monarchies being overthrown regularly and royal houses vying for supremacy over their lands. Wales had much survived the Anglo-Saxon invasion of Britain. But, unlike their neighbors in England. However, things would change dramatically during the Viking raids of the Cambro-Norse era (850s - 1100s). Raids included all sorts of pillaging and slave raids. A Welsh King would have to pay a ransom for the return of Welsh people. This era eventually ended through an alliance between the Welsh of Aberffraw and the Viking mercenaries of Scandinavian York, and then afterward, they allied with the Norse Vikings of Dublin. The reach of the Viking activity in Britain was not limited to the British nations on the Isles of the Northern Seas, including Wales; Ireland; Scotland, Hebrides and the Orkney Islands; Mann, and England. The Vikings also managed to travel to Eastern Europe. They co-founded the Kievan Rus (Ukraine & Russia), then also as far east as the Byzantine Empire. There were some assimilated (Harald III- Hardrada) in Asia Minor. Also to the south as far as Nekor, now in Morocco (Bjorn Ironside) for a slave raid in the Sahara Desert in Africa. Then, some Vikings would go on to discover and settle Iceland in the North Atlantic Ocean, some then voyaged westwards to Greenland (Erik the Red), and then successfully traveled west one last time to finish crossing the Atlantic Ocean (500 years before Columbus) where they settled L'Anse aux Meadows in Vinland (Canada) as part of the Norse colonisation of North America (Leif Erikson, c.1000 AD).

Image courtesy of Wiki Commons, attributed to Max Naylor, North Atlantic Viking expansion circa 8- 11th centuries.

After over 600 years of invasions by the Saxons, Danes, and Vikings, the map of the Brythonic Kingdoms changed drastically by the 11th century. The last Viking King in England was Harald III of Norway. The King was killed at the battle of Stamford Bridge in 1066. This event was one of 3 battles that marked the end of the Viking Age and the beginning of the French Norman dynasty. The then-new British royal family was founded in the 9th century by a Viking named Rollo, who became the Duke of Normandy. The Saxon and Viking family connections of the current ruling British Monarchy were still on display as recently as early the 20th century, when Maud the Princess of Wales became the Queen Consort of Norway. During the 19th to 20th centuries, the British royal family was named the Royal House of Saxe-Coburg and Gotha, a name from Germany. However, due to public sentiment due to the use of a German household name and the ongoing War situation in the European theatre of World War I, they were renamed Royal House to the House of Windsor (cadet branch).