Constantius III was a general under Honorius. It was thanks to him and his armies that the usurpers Constantine III, Constans II and Maximus were defeated and their domains returned to the empire. As recognition for these triumphs Honorius gave him his sister, Galla Placidia, in marriage and made him co-emperor in 421. However, Theodosius II out in the eastern half of the empire would not recognize Constantius. To assert his title, Constantius then prepared to take on Theodosius but became ill and died before plans could materialize. Galla became pregnant before his death and their son Valentinian III would in a few years become emperor himself.
RIC 1325 (X, Honorius) Solidus Obv: DNCONSTANTIVSPFAVG - Diademed, draped and cuirassed bust right. Rev: VICTORIAAVGGG Exe: R/V/COMOB - Constantius standing right, holding standard and Victory on globe, and trampling on captive. 421 (Ravenna). $24,400 1/16/02.