Western Roman in the context of "Arcadius"

The Huns were a nomadic people who lived in Central Asia, the Caucasus, and Eastern Europe between the 4th and 6th centuries AD. According to European tradition, they were first reported living east of the Volga River, in an area that was part of Scythia at the time. By 370 AD, the Huns had arrived on the Volga, causing the westwards movement of Goths and Alans. By 430, they had established a vast, but short-lived, empire on the Danubian frontier of the Roman empire in Europe. Either under Hunnic hegemony, or fleeing from it, several central and eastern European peoples established kingdoms in the region, including not only Goths and Alans, but also Vandals, Gepids, Heruli, Suebians and Rugians.

The Huns, especially under their King Attila, made frequent and devastating raids into the Eastern Roman Empire. In 451, they invaded the Western Roman province of Gaul, where they fought a combined army of Romans and Visigoths at the Battle of the Catalaunian Fields, and in 452, they invaded Italy. After the death of Attila in 453, the Huns ceased to be a major threat to Rome and lost much of their empire following the Battle of Nedao (c. 454). Descendants of the Huns, or successors with similar names, are recorded by neighboring populations to the south, east, and west as having occupied parts of Eastern Europe and Central Asia from about the 4th to 6th centuries. Variants of the Hun name are recorded in the Caucasus until the early 8th century.

Syagrius (c. 430 – 486 or 487 or 493–4) was a Roman general and the last ruler of a Western Roman rump state in northern Gaul, now called the Kingdom of Soissons. Gregory of Tours referred to him as King of the Romans. Syagrius's defeat by King of the Franks Clovis I is considered the end of Western Roman rule outside of Italy. He inherited his position from his father, Aegidius, the last Roman magister militum per Gallias. Syagrius preserved his father's territory between the Somme and the Loire around Soissons after the collapse of central rule in the Western Empire, a domain Gregory of Tours called the "Kingdom" of Soissons. Syagrius governed this Gallo-Roman enclave from the death of his father in 464 until 486, when he was defeated in battle by Clovis I.

Historians have mistrusted the title "Rex Romanorum" that Gregory of Tours gave him, at least as early as Godefroid Kurth, who dismissed it as a gross error in 1893. The common consensus has been to follow Kurth, based on the historical truism that Romans hated kingship from the days of the expulsion of Tarquin the Proud; for example, Syagrius's article in the Prosopography of the Later Roman Empire omits this title, preferring to refer to him as a "Roman ruler (in North Gaul)". However, Steven Fanning has assembled a number of examples of rex being used in a neutral, if not favorable, context, and argues that "the phrase Romanorum rex is not peculiar to Gregory of Tours or to Frankish sources", and that Gregory's usage may indeed show "that they were, or were seen to be, claiming to be Roman emperors."

Aegidius (died 464 or 465) was the ruler of the short-lived Kingdom of Soissons from 461 to 464/465. Before his ascension he was an ardent supporter of the Western Roman emperor Majorian, who appointed him magister militum per Gallias ("Master of the Soldiers for Gaul") in 458. After the general Ricimer assassinated Majorian and replaced him with Emperor Libius Severus, Aegidius rebelled and began governing his Gallic territory as an independent kingdom. He may have pledged his allegiance to the Eastern Roman emperor Leo I.

Aegidius repeatedly threatened to invade Italy and dethrone Libius Severus, but never actually launched such an invasion; historians have suggested he was unwilling to launch an invasion due to the pressure of the Aquitanian Goths, or else because it would leave Gaul exposed. Aegidius launched several campaigns against the Visigoths and the Burgundians, recapturing Lyon from the Burgundians in 458, and routing the Visigoths at the Battle of Orleans. He died suddenly after a major victory against the Goths; ancient historians say that he was assassinated, but do not give the name of the assassin, whereas modern historians believe it is possible that he died a natural death.