Constantius III was briefly Western Roman emperor in 421, having earned the throne through his capability as a general under Honorius. By 411 he had achieved the rank of magister militum, and in the same year he suppressed the revolt of the usurper Constantine III. Constantius went on to lead campaigns against various barbarian groups in Hispania and Gaul, recovering much of both for the Western Roman Empire. He married Honorius's sister Galla Placidia in 417, a sign of his ascendant status, and was proclaimed co-emperor by Honorius on 8 February 421. Constantius reigned for seven months before dying on 2 September 421.

Honorius was Roman emperor from 393 to 423. He was the younger son of emperor Theodosius I and his first wife Aelia Flaccilla. After the death of Theodosius in 395, Honorius, under the regency of Stilicho, ruled the western half of the empire while his brother Arcadius ruled the eastern half. His reign over the Western Roman Empire was notably precarious and chaotic. In 410, Rome was sacked for the first time in almost 800 years.