Shapur I, an ambitious organizer and statesman,…

Shapur I, an ambitious organizer and statesman, had in 240 or 241 become the Persian king of the Sassanian dynasty founded by his father: he has united his empire by bringing the Iranian lords into line and by protecting the Zoroastrian religion.

He also tolerates the Manichaeans and puts an end to the persecutions of the Christians and Jews, thereby gaining the sympathy of these communities.

Roman Emperor Hadrian had fixed the frontiers at the Euphrates, but under Nero, the Romans had claimed control over the kings of Armenia, and under Caracalla, they had annexed Osroëne and Upper Mesopotamia.

The Parthian empire had been weak and often troubled, but the Sassanids are more dangerous.