Murong Huang and his son Murong Jun, who initially claim the Jin Dynasty-created title "Prince of Yan," establish Former Yan, a state of Xianbei ethnicity, in 337.

Constantine had hoped to be baptized in the Jordan River, but perhaps because of the lack of opportunity to do so—together possibly with the reflection that his office necessarily involves responsibility for actions hardly compatible with the baptized state—he has delayed the ceremony.

It is while preparing for a campaign against Persia that he falls ill at Helenopolis.

When treatment fails, he makes to return to Constantinople, but …

…the emperor is forced to take to his bed near Nicomedia.

Here, Constantine receives baptism, putting off the imperial purple for the white robes of a neophyte; and he dies on May 22, 337.

He is buried at Constantinople in his Church of the Apostles, whose memorials, six on each side, flank his tomb.

This is less an expression of religious megalomania, however, than of Constantine's literal conviction that he was the successor of the evangelists, having devoted his life and office to the spreading of Christianity.

One of his final decrees had been the abolition of crucifixion within the Roman Empire.

The Syro-Christian populations of Mesopotamia and …

…Babylonia have begun to feel sympathy with Roman policies for religious reasons.

The Sassanian emperors have consequently felt the need to consolidate their Zoroastrianism, and efforts have been made to perfect and enforce state orthodoxy.

Shortly after 337, the Persian king Shapur II, determined to reconquer lost Persian territory to the east and west and to assert his own authority, takes an important policy decision.

Although the state religion of the Sassanian Empire is Mazdaism (Zoroastrianism), Christianity flourishes within its boundaries.

Constantine had granted toleration to Christians in 313, and with the subsequent Christianization of the empire, Shapur, mistrustful of a potential force of a fifth column at home while he is engaged abroad, orders the persecution and forcible conversion of the Christians; this policy will be in force throughout his reign.

All heresy is proscribed by the state, defection from the official faith is made a capital crime, and persecution of the heterodox, the Christians in particular, begins.

Competition between Iran and Rome-Constantinople thus takes on a religious dimension.

A new war is inevitable.

Seeing an opportunity in the death of Constantine, Shapur sends his forces across the Tigris River, the uneasy frontier, to recover Armenia and Mesopotamia, which his predecessors had lost to the Romans.

The Roman Empire has become Christian, and Christianity has become predominant in Armenia after its king had adopted the Christian faith in 294.

Constans, Constantine’s youngest son, who is sympathetic to the orthodox Christians, takes control of the central prefecture: Italy, Africa, and Illyricum.

Constantine II, at twenty the eldest of Fausta's three sons, retains the West, becoming the ruler of Britain, Gaul, and Spain.

He is sympathetic to the Arian Christians.

Li Shou, cousin to Cheng Han's founding emperor Li Xiong, overthrows Li Xiong's son Li Qi in 338, disassociates himself from Li Xiong's regime by renaming the state from Cheng to Han, and sets up a different imperial ancestral temple.

(Traditional historians did not consider his regime a separate state, however, and treated the succession from Li Xiong to Li Shou's son Li Shi as a single Cheng Han state.)

Constantine had been preparing to go to war against the Persians at the time of his death in 337.

This legacy weighs heavily on the shoulders of Constantius, a military incompetent when compared to the energetic Shapur, with whom Constantius in 338 becomes engaged in what will prove to be a dozen years of inconclusive but extremely bloody warfare.

The Emperor's death in 337 had allowed Athanasius to return to Alexandria, but Constantius renews the order of banishment in 338.