If a general, or war leader, or chieftain named Arthur actually existed he was either a Roman or someone who rose to power shortly after the fall of the Roman Empire.
In the Middle Ages, English knights joined the Crusades and traveled far and wide. As they made their way to Jerusalem and the battlefields of the Middle East, they encountered weapons made of Damascus Steel. These weapons were light, flexible and kept their edge. A Saracen sword would be something to be treasured and perhaps endow with mystical properties.
In the Excalibur Rising series of Arthurian time travel novels, I offer another compelling and much darker explanation of the origin of Excalibur and its relation to King Arthur. Book One and Book Two are now available and Book Three will be available in January.