When King Hormizd II died, the Persian magnates killed his eldest son, blinded the second, and imprisoned the third (Hormizd, who afterwards escaped to the Romans); the throne was reserved for the unborn child of one of the wives of Hormizd. This child, named Shapur, was therefore born king; the government was conducted by his mother and the magnates. But when Shapur came of age, he turned out to be one of the greatest monarchs of the dynasty.
Under his reign the collection of the Avesta was completed, heresy and apostasy punished, and the Christians persecuted. This was a reaction against the Christianization of the Roman empire by Constantine.
In 337, just before the death of Constantine, Shapur broke the peace concluded in 297 between Narseh and Diocletian, which had been observed for forty years, and a war of twenty-six years (337-363) began. Shapur attempted with varying success to conquer the great fortresses of Roman Mesopotamia: Singara, Nisibis (which he invested three times in vain), and Amida (Diarbekr).
The Roman emperor Constantius II was always beaten in the field. Nevertheless Shapur made scarcely any progress; the military power of his kingdom was not sufficient for a lasting occupation of the conquered districts. At the same time he was attacked in the east by nomad tribes, among whom the Chionites are named. After a prolonged struggle they were forced to conclude a peace, and their king, Grumbates, accompanied Shapur in the war against the Romans.
In 359, Shapur conquered Amida after a siege of seventy-three days, and he took Singara and some other fortresses in the next year. In 363 the emperor Julian, at the head of a strong army, advanced to Ctesiphon, but was killed. His successor Jovian was defeated and made an ignominious peace, by which the districts on the Tigris and Nisibis were ceded to the Persians, and the Romans promised to interfere no more in Armenia. In the rock-sculptures near the town Shapur in Persis (Stolze, Persepolis, p. 141) the great success is represented; under the hoofs of the king's horse lies the body of an enemy, probably Julian, and a suppliant Roman, the emperor Jovian, asks for peace.
Shapur now invaded Armenia, where he took king Arsaces III, the faithful ally of the Romans, prisoner by treachery and forced him to commit suicide. He then attempted to introduce Zoroastrian orthodoxy into Armenia. However, the Armenian nobles resisted him successfully, secretly supported by the Romans, who sent King Pap, the son of Arsaces III, into Armenia. The war with Rome threatened to break out again, but Valens sacrificed Pap, arranging for his assassination in Tarsus, where he had taken refuge (374). Shapur had conducted great hosts of captives from the Roman territory into his dominions, most of whom were settled in Susiana. Here he rebuilt Susa, after having killed the city's rebellious inhabitants, and founded some other towns. He was successful in the east, and the great town Nishapur in Khorasan (eastern Parthia) was founded by him.
This entry was originally from the 1911 Encyclopedia Britannica; it has been copyedited but not fact-checked or added to.