Constantius II - Augustus in The East

Augustus in The East

In early 337, Constantius hurried to Constantinople after receiving news that his father was near death. After Constantine died, Constantius buried him with lavish ceremony in the Church of the Holy Apostles. Soon after his father's death Constantius supposedly ordered a massacre of his relatives descended from the second marriage of his paternal grandfather Constantius Chlorus, though the details are unclear. Eutropius, writing between 350 and 370, states that Constantius merely sanctioned “the act, rather than commanding it”. The massacre killed two of Constantius' uncles and six of his cousins, including Hannibalianus and Dalmatius, rulers of Pontus and Moesia respectively. The massacre left Constantius, his older brother Constantine II, his younger brother Constans, and three cousins Gallus, Julian and Nepotianus as the only surviving male relatives of Constantine the Great. Soon after, Constantius met his brothers in Pannonia at Sirmium to formalize the partition of the empire. Constantius received the eastern provinces, including Constantinople, Thrace, Asia Minor, Syria, Egypt, and Cyrenaica; Constantine received Britannia, Gaul, Hispania, and Mauretania; and Constans, initially under the supervision of Constantine II, received Italy, Africa, Illyricum, Pannonia, Macedonia, and Achaea.

Constantius then hurried east to Antioch to resume the war with Persia. While Constantius was away from the eastern frontier in early 337, Shapur assembled a large army, including war elephants, and launched an attack on Roman territory, laying waste to Mesopotamia and putting Nisibis under siege. Despite initial success, Shapur lifted his siege after his army missed an opportunity to exploit a collapsed wall. When Constantius learned of Shapur's withdrawal from Roman territory, he prepared his army for a counter-attack, drilling them and upgrading the equipment of his cataphracts.

Constantius repeatedly defended the eastern border against invasions by the aggressive Sassanid Empire under king Shapur II. These conflicts were mainly limited to Sassanid sieges of the major fortresses of Roman Mesopotamia, including Nisibis (Nusaybin), Singara, and Amida (Diyarbakir). Although Shapur seems to have been victorious in most of these confrontations, the Sassanids were able to achieve little. However, the Romans won a decisive victory at the Battle of Narasara, killing Shapur's brother, Narses. Ultimately, Constantius was able to push back the invasion, and Shapur failed to make any significant gains.

Meanwhile, Constantine II desired to retain control of Constans' realm, leading the brothers into open conflict. Constantine was killed in 340 near Aquileia during an ambush. As a result, Constans took control of his deceased brother’s realms and became sole ruler of the Western two-thirds of the empire. This division lasted until 350, when Constans was assassinated by forces loyal to the usurper Magnentius.