Shapur II and Julian's Persian Expedition of AD 363

Julian’s Persian expedition was a Roman invasion of the Sasanian Empire in the spring and summer of AD 363. The emperor Julian led a large army down the Euphrates to the gates of the Persian capital, Ctesiphon, but could not take it and was mortally wounded during the retreat. His successor, Jovian, had to make peace with King Shapur II on harsh terms, handing over the great frontier fortress of Nisibis. It was one of Persia’s most important victories over Rome.

Background: a long frontier war

The Sasanian King of Kings Shapur II (reigned 309–379) came to the throne as an infant. Once of age, he set out to reverse the treaty of 299, by which his predecessor Narseh had been forced to give Rome five regions east of the Tigris after a heavy defeat.

From the late 330s Shapur fought a long, grinding war against Constantius II, the son of Constantine the Great. Its centre was northern Mesopotamia. Shapur besieged the Roman fortress city of Nisibis three times, in 338, 346 and 350, without success. In 359 he captured Amida (modern Diyarbakır) after a 73-day siege, described by the Roman officer and historian Ammianus Marcellinus, who escaped from the city.

Julian, Constantine’s nephew, had been proclaimed emperor by his troops in Gaul in 360. When Constantius died in 361, Julian became sole ruler. Famous for trying to restore the traditional gods in a Christianising empire, he is remembered as Julian the Apostate.

Julian’s plan

Julian prepared his campaign at Antioch over the winter of 362–363. He refused Persian offers to negotiate, according to the sources, and aimed at a decisive blow.

On 5 March 363 he left Antioch. His main army is usually estimated at about 65,000 men, though ancient figures vary. He sent a second force, often put at about 30,000, under his relative Procopius and the general Sebastianus, to operate in northern Mesopotamia and join the Armenian king Arsaces II.

Julian himself marched down the Euphrates, supported by a large fleet of river boats carrying supplies and siege equipment; Ammianus speaks of about 1,000 transport ships and 50 warships. The plan seems to have been for the two forces to meet near Ctesiphon, but the northern army never arrived.

The march to Ctesiphon

The advance went well at first. The army captured or bypassed fortified towns along the Euphrates, including Pirisabora and Maiozamalcha, which fell after hard sieges in May.

Shapur avoided a pitched battle. He let the Romans advance deep into his territory while his forces flooded fields, broke dykes and harassed the columns.

Near the end of May, the Romans crossed to the Tigris by a canal and fought their way across the river in a night attack. In front of Ctesiphon they defeated a Persian army, but the city’s walls were strong, and Shapur’s main army was approaching. Julian’s council decided that a siege was impossible.

Retreat and the death of Julian

Julian then took a fateful decision. He burned most of his fleet, which was hard to move upstream and needed thousands of men to tow, and marched inland along the east bank of the Tigris. Ancient writers suggest he hoped to reach the provinces of Corduene or meet the northern army.

The retreat became an ordeal in the summer heat. The Persians had burned crops in the army’s path, supplies ran short, and Persian cavalry and armoured troops attacked again and again.

On 26 June 363, during a sudden Persian attack near Samarra, Julian rushed into the fight without his breastplate. A cavalry spear pierced his side and entered his liver. He was carried to his tent, where he died that night at the age of 31 or 32.

Ammianus, who was with the army, describes Julian discussing the soul with philosophers as he died. Who threw the spear remained a mystery. The pagan orator Libanius later suggested a Christian in Julian’s own army was responsible; Christian writers credited divine punishment. Neither claim can be proved.

The peace of 363

The next day the army chose Jovian, an officer of the imperial guard, as emperor. With the army trapped and starving on the east bank of the Tigris, he accepted Shapur’s terms in early July. The peace was to last 30 years. Rome gave up:

• the five regions beyond the Tigris won in 299, including Arzanene, Moxoene, Zabdicene, Rehimene and Corduene;
• the fortress cities of Nisibis and Singara, which had been the heart of Roman defence in Mesopotamia;
• its alliance with Armenia, leaving the Armenian king Arsaces II exposed to Persia.

The Persians took Nisibis without its population. Its inhabitants were moved to Roman territory, mainly to Amida. Among them was the Syriac poet and theologian Ephrem, who settled in Edessa.

Jovian died in February 364, before he could return to Constantinople. Julian’s body was buried at Tarsus in Cilicia and was later moved to the Church of the Holy Apostles in Constantinople, the city founded by his uncle (see Founding of Constantinople).

Key people

• Julian (c. 331–363): emperor from 361, scholar and soldier who tried to revive the traditional cults.
• Shapur II (309–379): Sasanian King of Kings who defended Mesopotamia and won back the lands lost in 299.
• Jovian (c. 331–364): guards officer chosen as emperor, who signed the peace.
• Ammianus Marcellinus: Roman officer and historian who took part in the campaign and wrote the main account.
• Procopius: Julian’s relative, who commanded the northern army and later rebelled against Valens.

Legacy

The treaty of 363 fixed the Roman-Persian frontier in Mesopotamia for more than two centuries. Nisibis became an important Persian city and later a centre of the Church of the East, while Rome built up Dara and other fortresses to replace it.

For Shapur, the victory was the high point of a reign that lasted seventy years. A Sasanian relief at Taq-e Bostan near Kermanshah, carved for his successor Ardashir II, shows a fallen enemy trampled underfoot; many scholars identify him as Julian, though this is debated.

In Christian tradition Julian’s death became a moral story about the failure of a pagan emperor. The famous dying words “You have conquered, Galilean” appear only in the 5th-century historian Theodoret and are considered a legend.

Julian’s campaign is often compared with the defeat of Crassus at Carrhae and the capture of Valerian at the Battle of Edessa. Together these events show how difficult it was for Rome to win decisive victories against Iranian powers on their own ground.

Timeline

• 299: Treaty of Nisibis gives Rome five regions beyond the Tigris.
• 309: Shapur II becomes King of Kings as an infant.
• 338, 346 and 350: Shapur besieges Nisibis without success.
• 359: Shapur captures Amida.
• 363, 5 March: Julian leaves Antioch.
• 363, May: Romans take Maiozamalcha and win a battle before Ctesiphon.
• 363, June: Julian burns his fleet and begins the retreat along the Tigris.
• 363, 26 June: Julian is mortally wounded and dies that night.
• 363, early July: Jovian agrees peace with Shapur II.

Why it matters

Julian’s failed expedition was the last great Roman offensive into Mesopotamia for centuries. It cost Rome its emperor, the key fortress of Nisibis and its hold on Armenia, and confirmed Sasanian Persia under Shapur II as Rome’s equal in the East.