Non-specialists continue to propose a variety of theories for a possible historical identity of Arthur: Artuir mac Áedán, a son of the 6th-century king of Dál Riata in modern Scotland; Ambrosius Aurelianus, who led a Romano-British resistance against the Saxons; Lucius Artorius Castus, a 2nd-century Roman commander of Sarmatian cavalry; the British king Riothamus, who fought alongside the last Gallo-Roman commanders against the Visigoths in an expedition to Gaul in the 5th century. Academic historians have not supported these hypotheses in the 21st century.