The legend of King Arthur is an intricate blend of history, folklore, and myth that has evolved significantly from its ancient origins. While the popular image of Arthur as a noble king leading the Knights of the Round Table has medieval roots, the basis of his legend can be traced back to ancient Britain, influenced by Roman military traditions, Celtic mythology, and early Christian ideals. This article explores these ancient roots, examining historical and archaeological sources, such as Historia Brittonum and the Annales Cambriae, which depict Arthur as a "dux bellorum" or military leader rather than a king. These sources link Arthur to battles against Saxons, with notable sites like Cadbury Castle supporting the theory of a Romano-British chieftain defending against external threats.

Celtic mythology deeply impacts Arthur’s image, with figures from Welsh and Irish folklore, such as Cú Chulainn and Culhwch, paralleling Arthur’s story in their heroic attributes. The symbolism of Excalibur reflects Celtic traditions of enchanted weapons, such as the Welsh Caledfwlch and Irish Claidheamh Soluis, enhancing Arthur’s image as a warrior with divine support. The Roman influence emerges in theories positioning Arthur as a Roman or Romano-British leader within a cultural landscape shaped by Roman governance and military strategies, particularly after Rome's withdrawal from Britain. Scholars suggest that Arthur could belong to a Romanized family, possibly connected to the name “Artorius,” a popular Roman name linked to the second-century military leader Lucius Artorius Castus. This connection underpins Arthur’s character as a Roman-style commander preserving stability during chaotic times.

As Christianity spread in Britain, early Christian monks incorporated Christian virtues into Arthurian lore. This shift culminates in the Grail legend, where Arthur’s pursuit of the Holy Grail mirrors early Christian ideals, combining Christian purity with pre-Christian Celtic symbols of magical cauldrons. Early writers such as Gildas indirectly contributed to this virtuous leader archetype by contrasting Arthur’s morality with the corrupt rulers of the time.

In the modern era, Howard Pyle’s adaptations, notably The Story of King Arthur and His Knights (1903), transformed Arthur into a figure embodying chivalric ideals of honor, duty, and moral integrity. Pyle’s works recast Arthur as a compassionate, just ruler whose court is a symbol of unity and moral leadership. His illustrations of Camelot and the Round Table set a visual standard that continues to shape Arthur’s image in popular culture, portraying a timeless utopia of bravery and noble values.

The enduring appeal of King Arthur lies in his adaptability, allowing him to resonate as a cultural symbol of resilience and unity. Through centuries of storytelling, Arthur has evolved from a Romano-British leader to a mythic king, embodying both ancient traditions and contemporary ideals of justice and valor.