According to the Chronicon Albeldense, included in the Códice de Roda, Wallia was desperate for food supplies.
He surrendered to Constantius III, at the time magister militum of Honorius, negotiating terms giving foederati status for the Visigoths.
Placidia was returned to Honorius as part of the peace treaty.
Her brother Honorius forced her into marriage to Constantius III on January 1, 417.
Their daughter Justa Grata Honoria was probably born in 417 or 418.
The history of Paul the Deacon mentions her first among the children of the marriage, suggesting that she was the eldest.
Their son Valentinian III was born July 2, 419.

Placidia intervened in the succession crisis following the death of Pope Zosimus on December 26, 418.
Two factions of the Roman clergy had proceeded to elect their own popes, the first electing Eulalius (December 27) and the other electing Boniface I (December 28).
They acted as rival popes, both in Rome, and their factions plunged the city into tumult.
Symmachus, Prefect of Rome, sent his report to the imperial court at Ravenna, requesting an imperial decision on the matter.
Placidia and, presumably, Constantius petitioned the emperor in favor of Eulalius.
This was arguably the first intervention by an Emperor in the Papal election.

Honorius initially confirmed Eulalius as the legitimate pope.
As this failed to put an end to the controversy, Honorius called a synod of Italian bishops at Ravenna to decide the matter.
The synod met from February to March 419 but failed to reach a conclusion.
Honorius called a second synod in May, this time including Gaulish and African bishops.
In the meantime, the two rival popes were ordered to leave Rome.
As Easter approached, however, Eulalius returned to the city and attempted to seize the Basilica of St. John Lateran in order to "preside at the paschal ceremonies".
Imperial troops managed to repel him, and on Easter (March 30, 419) the ceremonies were led by Achilleus, Bishop of Spoleto.
The conflict cost Eulalius the imperial favor, and Boniface was proclaimed the legitimate pope as of April 3, 419, returning to Rome a week later.
Placidia had personally written to the African bishops, summoning them to the second synod.
Three of her letters are known to have survived.

On February 8, 421, Constantius was proclaimed an Augustus, becoming co-ruler with the childless Honorius.
Placidia was proclaimed an Augusta.
She was the only Empress in the West, since Honorius had divorced his second wife Thermantia in 408 and had never remarried.
Neither title was recognised by Theodosius II, the Eastern Roman Emperor.
Constantius reportedly complained about the loss of personal freedom and privacy that came with the imperial office.
He died of an illness on September 2, 421.
According to the Chronicon Albeldense, included in the Códice de Roda, Wallia was desperate for food supplies. He surrendered to Constantius III, at the time magister militum of Honorius, negotiating terms giving foederati status for the Visigoths. Placidia was returned to Honorius as part of the peace treaty. Her brother Honorius forced her into marriage to Constantius III on January 1, 417. Their daughter Justa Grata Honoria was probably born in 417 or 418. The history of Paul the Deacon mentions her first among the children of the marriage, suggesting that she was the eldest. Their son Valentinian III was born July 2, 419.
Placidia intervened in the succession crisis following the death of Pope Zosimus on December 26, 418. Two factions of the Roman clergy had proceeded to elect their own popes, the first electing Eulalius (December 27) and the other electing Boniface I (December 28). They acted as rival popes, both in Rome, and their factions plunged the city into tumult. Symmachus, Prefect of Rome, sent his report to the imperial court at Ravenna, requesting an imperial decision on the matter. Placidia and, presumably, Constantius petitioned the emperor in favor of Eulalius. This was arguably the first intervention by an Emperor in the Papal election.
Honorius initially confirmed Eulalius as the legitimate pope. As this failed to put an end to the controversy, Honorius called a synod of Italian bishops at Ravenna to decide the matter. The synod met from February to March 419 but failed to reach a conclusion. Honorius called a second synod in May, this time including Gaulish and African bishops. In the meantime, the two rival popes were ordered to leave Rome. As Easter approached, however, Eulalius returned to the city and attempted to seize the Basilica of St. John Lateran in order to "preside at the paschal ceremonies". Imperial troops managed to repel him, and on Easter (March 30, 419) the ceremonies were led by Achilleus, Bishop of Spoleto. The conflict cost Eulalius the imperial favor, and Boniface was proclaimed the legitimate pope as of April 3, 419, returning to Rome a week later. Placidia had personally written to the African bishops, summoning them to the second synod. Three of her letters are known to have survived.
On February 8, 421, Constantius was proclaimed an Augustus, becoming co-ruler with the childless Honorius. Placidia was proclaimed an Augusta. She was the only Empress in the West, since Honorius had divorced his second wife Thermantia in 408 and had never remarried. Neither title was recognised by Theodosius II, the Eastern Roman Emperor. Constantius reportedly complained about the loss of personal freedom and privacy that came with the imperial office. He died of an illness on September 2, 421.
Galla Placidia