Born as Khosrow, son of Shah Kavadh I, within the Sasanian court culture shaped by Zoroastrian ritual and aristocratic rivalry. His early years unfolded amid factional struggles that later motivated his drive for order and reform.

As a young prince, he was trained by court scholars and veteran nobles in statecraft, law, and military command. Exposure to debates over Mazdakite social teachings taught him how ideology could destabilize the realm.

In the late years of Kavadh I, Khosrow aligned with traditional nobles and the Zoroastrian priesthood to roll back Mazdakite redistribution policies. The episode convinced him that strong administration was essential to prevent sectarian upheaval.

After Kavadh I died, Khosrow secured the throne amid succession tension among princes and powerful magnates. He styled himself a restorer of justice, presenting kingship as guardianship over both nobles and commoners.

He negotiated a major settlement with Byzantine emperor Justinian I, ending the Iberian War and stabilizing the western frontier. The agreement brought payments to Persia and freed resources for internal reforms and eastern defense.

Khosrow reorganized assessment by linking taxes to surveyed land and productivity, reducing arbitrary collection by local powerholders. Officials and scribes created more predictable revenue streams, strengthening the army and central court finances.

He strengthened the spah (army) with clearer chains of command and more reliable pay supported by the new tax system. Frontier defenses were reinforced to counter both Byzantine raids and steppe pressures on the Caucasus approaches.

Breaking peace with Justinian I, Khosrow marched into Syria and captured Antioch, a prized Roman metropolis. He deported many inhabitants and used the victory to project Sasanian prestige and extract wealth from Byzantine provinces.

Near Ctesiphon he established a new city, often called 'Khosrow's Better Antioch,' to house deportees from Antioch under royal supervision. The project showcased planned urbanism and the king’s claim to be a just, organizing ruler.

Campaigns in northern Mesopotamia threatened key Byzantine strongholds and compelled diplomacy under the shadow of siege warfare. The resulting arrangements brought tribute-like payments and preserved Persian leverage along the frontier corridor.

His court patronage bolstered the intellectual reputation of Gundeshapur, where physicians and translators drew on Greek, Syriac, and Persian learning. Royal interest in practical sciences strengthened administrative expertise and medical services for the elite.

Sasanian forces supported allies in Yemen, contesting the Red Sea trade routes influenced by the Aksumite kingdom and Byzantine interests. The intervention extended Persian reach into Arabian geopolitics and secured strategic maritime connections.

Khosrow navigated shifting steppe alliances, confronting threats from nomadic confederations and negotiating to stabilize the northeast. These policies protected Silk Road corridors and maintained revenue from transcontinental commerce.

A major treaty with the Byzantine Empire formalized frontier arrangements and included agreed payments for defense of key passes. The settlement aimed to reduce costly campaigning and let both empires address internal and regional challenges.

Late in his reign, Persian authority was consolidated around Gulf trade, linking Mesopotamian wealth to maritime routes. Administrative appointments and garrisons helped integrate coastal commerce with the imperial fiscal system.

Frontier tensions and political mistrust reignited conflict, drawing Sasanian forces back into prolonged western campaigning. The renewed war tested the durability of his reforms by demanding sustained logistics and coordinated command.

In his final years he prepared the transition to his son Hormizd IV, aiming to keep nobles and military commanders loyal to the crown. Court discipline and fiscal stability were emphasized to prevent a relapse into factional domination.

Khosrow I died after decades of reform, warfare, and cultural patronage that elevated Sasanian state capacity and prestige. Chroniclers remembered him as 'Anushirvan the Just,' a benchmark for later Persian ideals of kingship.