The Six Frontier Towns, also known as Northern Frontier Towns, refers to six military towns that the Northern Wei government has built during the Huangshi era and the Yanhe era to prevent the southward invasion by the Rouran Khaganate.

These towns, from west to east, are Woye, Huaishuo, Wuchuan, Fumin, Rouxuan and Huaihuang.

The official Li Chong sees that the people of the six northern military garrisons, largely ethnic Xianbei, who have for generations been forced to stay at these garrisons to defend against Rouran attacks, are stirring with discontent, and in 523 he suggests to Yuan Cha and Emperor Xiaoming that the garrisons be converted into provinces and that the people be given the rights of the people of other provinces.

Yuan Cha refuses.

Later this year, …

…the people of Huaihuang (in modern Zhangjiakou, Hebei) and …

…Woye (in modern Baynnur, Inner Mongolia) Garrisons rebel—rebellions that Northern Wei forces cannot quickly quell, and the rebellions soon spread throughout not only the six garrisons but throughout virtually the entire empire.

The more important rebels include Poliuhan Baling, with his rebellion concentrated around Woye; …

…Hu Chen, Tiele tribal chief, with his rebellion concentrated around Gaoping Garrison (in modern Guyuan, Ningxia); and …

…Mozhe Dati, with his rebellion concentrated around Qin Province (roughly modern Tianshui, Gansu), later succeeded by his son Mozhe Niansheng, who will declare himself Emperor of Qin.

Justin, the commander of the palace guard, had secured the imperial throne on the death of Emperor Anastasius in July 518.

Unlike his predecessor, Justin supports orthodoxy, and in 518-519 had been instrumental in ending the Acacian schism with Rome and persecutes the dissident Monophysites.

In 523, he also issues an edict against Arianism.

This offends the Arian king Theodoric of the Ostrogoths, who forces Pope John I to visit Constantinople to plead for a mitigation of the edict.

Justin then grants some concessions to the Arians but not enough to satisfy Theodoric.

In the East, the struggle with Persia makes it important for Constantinople to retain control of the small Christian kingdom of Lazica (modern Colchis, a region in Georgia), to secure allies in Mesopotamia and southern Syria, and to counter Persian penetration into Arabia by an understanding with Ethiopia.

On the northern frontier, the Slavs are already crossing the Danube River and troubling the Balkan provinces, and Justin proves unable to repel them.

Internal disorders and changing trade routes have caused the Himyar kingdom to suffer political and economic decline.

In 516, Himyarite ruler Yusuf As'ar Yath'ar, who is known in Arabic tradition mostly by the nickname Dhu Nuwas, had proclaimed himself a Jew, possibly as a rampart against the encroaching Christian faith.

Some sources state that he was the successor of Rabī'ah ibn Mudhar, a member of the same dynasty; the archeologist Alessandro de Maigret believes he was a usurper.

Nashwad bin Sa'īd al-Ḥimyarī stated that he killed his predecessor with a stiletto hidden in his sandal while his predecessor was seducing the handsome Yūsuf in his chambers.

According to a number of medieval historians, who depend on the account of John of Ephesus, Dhū Nuwās, announced that he would persecute the Christians living in his kingdom because Christian states persecuted his fellow co-religionists in their realms; a letter survives written by Simon, the bishop of Beth Arsham in 524, recounting Dhū Nuwās' (where he is called Dimnon) persecution in Najran (modern al-Ukhdūd in Saudi Arabia).

The persecution is apparently described and condemned in the Qur'an (al-Buruj:4).

Dhu Nuwas, after seizing the throne of the Ḥimyarites in about

518 or 523 according to the contemporary sources, attacked the Aksumite (mainly Christian Ethiopians and Yemeni Arab Christians) garrison at Zafar, capturing them and burning their churches.

He now moves against ...

...Najran, a Monophysite Christian and Aksumite stronghold.

After accepting the city's capitulation, he massacres those inhabitants who will not renounce Christianity.

Estimates of the death toll from this event range up to twenty thousand in some sources.

…Sigismund dons a monk's habit and hides in a cell near his abbey.

He is captured by Chlodomer, king of Aurelianum (modern Orléans), and taken prisoner to Aurelianum.