Byzantine–Sasanian War of 572–591 participant Ghassanids
Fall of Dara
In Mesopotamia, however, the war began disastrously for the Byzantines. After a victory at Sargathon in 573, they laid siege to Nisibis and were apparently on the point of capturing this, the chief bulwark of the Persian frontier defences, when the abrupt dismissal of their general Marcian led to a disorderly retreat. Taking advantage of Byzantine confusion, Sassanid forces under Khosrow I (r. 531–579) swiftly counter-attacked and encircled Dara, capturing the city after a four-month siege. At the same time, a smaller Persian army under Adarmahan ravaged Syria, sacking Apamea and a number of other cities. They were only pushed away from Syria proper by a bumbling Byzantine defence near Antioch. To make matters worse, in 572 the Byzantine emperor Justin II (r. 565-578) had ordered the assassination of the Ghassanid king al-Mundhir III; as a result of the unsuccessful attempt on his life, al-Mundhir severed his alliance with the Byzantines, leaving their desert frontier exposed.The fall of Dara, the main Byzantine stronghold in Mesopotamia, reportedly drove Justin II to insanity, and control of the Byzantine Empire passed to his wife Sophia and Tiberius Constantine. The new regents agreed to pay 45,000 nomismata for a one-year truce, and later in the year extended this to five years, secured by an annual payment of 30,000 nomismata. However, these truces applied only to the Mesopotamian front; in the Caucasus, the war continued.