# Constantius III

Constantius III (died 2 September 421) 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.

## Life
### Early life

Constantius was born in Naissus, Moesia, (present-day Niš, Serbia) of Illyrian origin. Constantius served as a general under Honorius, rising to the rank of Magister militum (Master of the Soldiers) by 411.

### Revolt of Constantine III

In 411 Constantius was sent by Honorius to put down the revolt of Constantine III, who had declared himself emperor in Britain in 407. Constantius thereafter led his soldiers to Arles, the capital and residence of Constantine. Upon arriving, he defeated the army of Gerontius, a general who was rebelling against Constantine, before besieging the city.
Constantine refused to surrender, hoping to last until the return of his general Edobichus, who was raising troops in northern Gaul. When Edobichus did return to Arles, he was swiftly defeated by Constantius. Constantine soon after lost much of the remainder of his forces, as his army which had been guarding the Rhine chose to support the usurper Jovinus instead, forcing Constantine to surrender. Despite Constantius's assurances that Constantine would be able to safely retire to a clerical office, Constantius had him imprisoned, and further had him beheaded during his return to Ravenna, in either August or September 411. Honorius's remaining rivals were soon defeated, with Gerontius committing suicide in Hispania, and Jovinus being defeated by Athaulf, king of the Visigoths. Despite this, Honorius was unable to regain control of Britain, nor was any Roman after him.

### The war against Heraclianus

The appointment of Constantius as commander-in-chief led to a war in 412 with the rival general Heraclianus, who, like Constantius, had done good services for Emperor Honorius. Heraclianus revolted, appointed himself emperor and stopped grain supplies to Italy. At the beginning of March 413, the usurper landed in Italy near Rome with an army to go to war against Honorius. He engaged in a battle with Constantius's Roman army, but was defeated. After his defeat, Heraclianus fled. He was captured and murdered.

### Campaigns

Constantius initiated a campaign against the Visigoths in northern Hispania in 416, blockading them in order to starve them and force their submission. Soon after, the Visigoth king, Wallia, surrendered to Rome, agreeing to return Galla Placidia (the sister of Honorius, who had been captured by Alaric c. 412, and been forced into marriage with Athaulf, who was by this time dead), and to wage war against the Vandals and other barbarians who the Romans were still in conflict with, in exchange for food supplies. This development enabled Constantius to put an end to the Bagaudae revolt in northwestern Gaul in 417. He then continued his campaign against various tribal groups and regained control of much of Hispania and Gaul by 420.

### Reign

During this time period, generals played a critical role in ensuring the continued reign of Roman Emperors, especially Western Roman Emperors. Constantius's position of magister militum and his skill as a commander allowed him to gain huge influence over the Western Roman Empire, comparable to the earlier Stilicho. For this reason, Honorius bestowed many honors upon Constantius, such as appointing him consul three times: in 414, alongside Constans; in 417, alongside Honorius; and in 420, alongside Theodosius II. In order to further ensure Constantius's loyalty, Honorius arranged the betrothal of his sister, Galla Placidia, to Constantius in 417. Later, on 8 February 421, Honorius made Constantius co-Western Emperor under himself. However, his cousin Theodosius II, emperor of the Eastern Empire, did not recognize him as such. Reportedly, Constantius was angry about this and considered starting a campaign against Theodosius.

### Death

In the end, none of that came to fruition, because Constantius' health deteriorated rapidly and he died after less than 7 months as emperor on 2 September 421. According to Syvänne, Constantius was killed by poisoning. As source, he cites Theophanes (AM 5913) who states that Constantius was murdered. Castinus, a confidant of Emperor Honorius, who after Constantius' death obtained the rank of commander-in-chief, is said to have had the hand in this. After his death, his wife fled with her children to Constantinople. Honorius only continued to reign until his death in 423, when Valentinian III, the minor son of Constantius, succeeded him, with Galla Placidia as regent.