<P> King Arthur is a legendary British leader who , according to medieval histories and romances , led the defence of Britain against Saxon invaders in the late 5th and early 6th centuries AD . The details of Arthur 's story are mainly composed of folklore and literary invention , and his historical existence is debated and disputed by modern historians . The sparse historical background of Arthur is gleaned from various sources , including the Annales Cambriae , the Historia Brittonum , and the writings of Gildas . Arthur 's name also occurs in early poetic sources such as Y Gododdin . </P>
when did the story of king arthur take place
late 5th and early 6th centuries AD