King Arthur is a fable British leader who, according to medieval histories and romances, led the defence of Britain against the Saxon invaders in the early 6th century. 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 histories, including those of Gildas, Nennius, and the Annales Cambriae. Arthur's name also occurs in early poetic sources such as Y Gododdin.