Political fragmentation retards cultural development in China.

China’s Nanjing-based Eastern Jin Dynasty is eliminated in 420.

The Northern Wei Dynasty unifies the Northern portion of the Chinese Empire, which will have three competing dynasties—Northern Wei, Northern Yan and Northern Liang, while …

…the Song (or Liu Song) Dynasty dominates the Southern state; Nanjing is reinstated as the capital.

The Huns under leadership of the brothers Octar and Rugila expand their rule through neighboring tribal groups.

Abdas, Bishop of Susa, engaged in a dispute with the local magi in 420, is accused of burning down one of their temples, a pyramid of Ahura Mazda.

King Yazdegerd orders the bishop to restore and repair the building at his own expense.

Upon Abdas' refusal, the King orders the destruction of the churches.

These events sour the good relationship between the Christian church and the Persian government and causes a wave of persecution against the Christians in Persia.

A new treaty with Rome results in the widowed Galla Placidia’s return and a pledge by the Visigoths, in exchange for food subsidies, to attack the Alans and Vandals in Spain.

The Visigoths break their peace with Rome in 420, however, by assisting the Vandals in a battle.

Fan Yang Mai, following years of internal trouble, overthrows the previous dynasty and seizes the Cham throne in 421.

Rugila, chieftain of the Huns, attacks the dioceses of Dacia and Thrace in the Balkans.

Theodosius II allows Pannonian Ostrogoths to settle in Thrace, to defend the Danube frontier.

The court over which Pulcheria presides is characterized by extreme piety and chastity.

She arranges the marriage of her brother, the emperor, to Athenais, who came from Athens, where her father, Leontius, is a pagan philosopher.

Before she and Theodosius are married (in June 421), Athenais is baptized a Christian and changes her name to Eudocia.

The wedding is celebrated at Constantinople with chariot racing in the Hippodrome.

Theodosius, a weak emperor more interested in scholarly pursuits, allows others, such as Pulcheria and Eudocia, to influence state decisions.

Yazdegerd has tried to emancipate himself from the dominion of the magnates and of the Magi (a priestly caste serving a number of religions); thus, Christian and Zoroastrian sources view his reign differently.

Because he had stopped the persecution of the Christians, the Christian writers praise his clemency, but the sources dependent on Zoroastrian tradition refer to him as “Yazdegerd the Sinner.” He has also tried to limit the power of the nobles, but had finally answered their resistance with severity.

He has lived in peace and friendship with the Roman Empire and is therefore praised by Greek authors.

He appears to have been murdered in Khorasan, after which the nobles refuse to admit any of his sons to the throne.

However, one of them, Bahram, has the support of al-Mundhir, Lakhmid Arab king of Al-Hirah in Mesene (east of the lower Euphrates) and a Sassanian vassal, and also, apparently, of Mihr-Narseh, chief minister in Yazdegerd's last years, who is retained in office.

After Yazdegerd's death in 421, Persian nobles try to reclaim Bahram from Mundhir, so Mundhir sends his son Nu'man ahead with a brigade, then personally escorts Bahram with another brigade of 20,000 soldiers to Ctesiphon, where the nobles, after some negotiations, acknowledge Bahram as their ruler.

Bahram V, known as Gor (“the wild ass,” for his prowess in hunting the onager, reverses his father‘s policy of religious toleration, and revives the violent persecution of Christians in the Persian empire.