The war erupted in 572 when Justin II abrogated the peace treaty of his predecessor and refused to pay the humiliating annual tribute to Khosrow I. However, early Byzantine offensives faltered, and in 573, the vital fortress of Dara fell to the Persians. Dara was Byzantium's principal stronghold on the Mesopotamian frontier, designed to counter nearby Nisibis and secure key military supply routes. Around this time, Justin II developed a severe mental illness, rendering him incapable of ruling. With the emperor incapacitated, Tiberius II stepped in as regent to manage the crisis.
Under Tiberius II and his capable general Maurice, the Byzantines stabilized the crumbling front. The conflict devolved into a grueling war of attrition, with raids and counter-raids trading blows across Mesopotamia and Armenia. In 586, the new Byzantine commander Philippicus achieved a major tactical victory at the Battle of Solachon. By cutting off the Sasanian cavalry's water supply, the Byzantines decisively defeated them, successfully halting further massive Persian offensives in Mesopotamia and greatly restoring the shattered morale of the Byzantine army. However, a strategic breakthrough remained elusive for both empires, and the long war of attrition continued.
The deadlock was broken not on the battlefield, but by a civil war within the Sasanian Empire. In 590, the Persian general Bahram Chobin rebelled, deposing King Hormizd IV and seizing the throne. Hormizd's son, Khosrow II, fled for his life to the court of his traditional enemy, the Byzantine Empire, pleading for Emperor Maurice's aid.
Maurice seized this opportunity to end the war on favorable terms. He agreed to support Khosrow II in exchange for significant territorial concessions. In 591, a combined Byzantine-Persian loyalist army defeated the usurper Bahram Chobin and restored Khosrow to his throne. True to his word, Khosrow ceded Dara, Martyropolis, and most of Persarmenia and Iberia to Maurice. The war concluded with a resounding Byzantine victory, extending the empire's eastern frontier to its greatest extent in centuries.