As Germanic, Alanic, and Hunnic peoples in invade the northern territories of the Roman Empire, Persia's northern borders are threatened first by a number of Hunnic peoples and then by the Hephthalites.

With both empires preoccupied by these threats, a largely peaceful period follows, interrupted only by two brief wars, the first in 421–422; the second will occur in 440.

Following the persecution of Christians in the Persian Empire by the Sassanid king Bahram V, which had come as a response to attacks by Christians against Zoroastrian temples; the Christian Eastern Roman Emperor Theodosius II declares war in 421 and obtains some victories, but in the end the two powers agree in 422 to sign a peace on the status quo ante.

Communication between Constantinople and Ctesiphon results in a one hundred-year peace, wherein the Persian ruler agrees to tolerate Christianity throughout the Sasanid empire; the Romans reciprocate by agreeing to tolerate Zoroastrianism throughout the Roman empire.