What did king Arthur do as king?

Answer 1

Unknown! We do not even know if there was a King Arthur. Most historians believe the legend derives from a dark age warlord 5-6th century who halted the advance of the Saxon invaders across Britain

Better AnswerArthur may not have been a "king" but the evidence seems to support the existence of someone called Arthur or Arturius who was a battle leader among the Britons in the late 5th Century and early 6th Century AD. He is said to have fought twelve battles against the invading Anglo-Saxons and at each battle he was victorious. According to Nennius and other medieval sources Arthur fought the following battles;

1) On the River Glein (probably somewhere in Cambridgeshire)

2, 3, 4 & 5) On the River Dubglas in the region of Linnuis (Lincolnshire)

6) On the River Bassas (unknown)

7) In the Forest of Celidon (southern Scotland)

8) Castle Guinnon (unknown)

9) City of the Legion (probably Chester)

10) On the River Tribruit (unknown)

11) At Mount Agned (unknown)

12) At Mount Badon (517AD, probably Barbury Rings) - here the Anglo-Saxons were slaughtered and the threat to Britain that they posed was removed for about 50 years.

Then there is the final battle at Camlann (538AD) where Arthur was betrayed and is mortally wounded. This battle does not appear in Nennius.

Without Arthur, Britain would have been conquered far sooner than it was by the English and this would have made the British Isles a profoundly different place than they are today.

Answer 2

King Arthur led the defense of Britain against Saxon invaders in the 6th century.