King Arthur is the best known name in English History, which is strange, because you would be hard pressed to find a historical figure with less historical evidence.
The story of King Arthur begins in 410, when the Roman Emperor sent a message to the island of Britain, telling the people that they must look after their own defence. For hundreds of years, Britain had lived mostly peacefully under Roman rule, now they were on their own. The people who lived in the region now known as England were called the Romano-British by history, being mostly Celtic in blood, but Roman in culture. With the fall of Roman rule, these people came under constant attack from their Celtic neighbours, notably the Welsh and the Picts (the natives of Scotland).
Although abandoned by Rome, the Romano-British were not without leaders, and foremost among them was a man named Vortigern. In response to increasing Celtic raids, Vortigern brought in Germanic mercenaries, the first major groups of Anglo-Saxons to arrive in England. For years, these warriors held the Celts at bay. Then, around the middle of the fifth century, things collapsed. Plague spread across the island, central authority collapsed, and the Anglo-Saxon mercenaries saw an opportunity for conquest and sent for their kinsmen. The famed warriors, Hengst and Horsa, soon arrived with a large Anglo-Saxon army and set about carving their own empire out of Britain.
Into this dark time, the figure of Ambrosius Aurelianus arose. Traditionally, Ambrosius was a Roman cavalry commander, but considering the time period in which he operated, he would have been very old to have served in any actual Roman Army, at least in Britain. Still, it is likely that he still used Roman strategy and tactics. He became a leader and a rallying point for the Romano-British who were now under attack from every side. Ambrosius organized a new defensive strategy based around the old hill forts of pre-Roman Britain. From these bases, the Romano-British were able to rebuild their military strength and eventually go back on the offensive.
But who lead this offensive? Almost certainly it started under Ambrosius Aurelianus, but soon thereafter, the name Arthur is used. It is possible that Arthur is some kind of shortened form of Ambrosius Aurelianus, but if so, no one has been able to show any real linguistic connection between the two names. It is interesting to note that of the shadowy historical time called the "Dark Ages" the time period of King Arthur is probably the darkest of all. There are virtually no records dating from anywhere near this time. The historical record basically gives us two clues, a note saying that Arthur defeated the Anglo-Saxons at a battle near Mount Badon, and a poem about someone else that states, "though he slew many foes, he was no Arthur."
So, perhaps he was Ambrosius Aurelianus, perhaps he was a completely different person named Arthur, we are unlikely to ever know the truth. What we do know is that under the leadership of Arthur, the Romano-British became the only group in western Europe able to stop the Germanic invasion, for a time anyway. It is quite possible that Arthur even managed to forge an alliance with the other native tribes of Britain, especially the Welsh, as many of the earliest tales of King Arthur are preserved in Welsh literature.
Although it is impossible to say the exact deeds of this man Arthur, it is safe to say they must have been great. His name has echoed down through British history louder than any other. In the end, everything he built would crumble away. The Anglo-Saxons would slowly overrun England, killing, or more likely assimilating the native Romano-British, and yet Arthur's stories were told, remembered and passed on, even by the people he successfully fought against.
