Battle of Ctesiphon (363)

The Battle of Ctesiphon took place on May 29, 363 between the armies of Roman Emperor Julian and the Sassanid King Shapur II outside the walls of the Persian capital Ctesiphon. The battle was a Roman tactical victory, although Julian was killed following the subsequent Battle of Samarra and the Roman forces found themselves unable to continue their campaign as they were too far from their supply lines.

Background
On November 3, 361, Constantius II died in the city of Mobsucrenae, leaving his cousin Flavius Claudius Julianus, known to history as Julian the Apostate, as sole Emperor of Rome. Arriving at Constantinople to oversee Constantius' burial, Julian immediately focused on domestic policy and began to greatly reform the Roman Imperial government by reorganizing, streamlining and reducing the bureaucracy.

Turning next to foreign policy, Julian saw the previously unchecked military incursions of Shapur II of Persia against the Eastern Roman provinces as posing the greatest external threat. After many failed earlier attempts, the Persian king launched a more successful second campaign against the Romans and captured Amida in 359, controlling the headwaters of the Tigris and the entrance to Asia Minor from the east. A Roman offensive was desperately needed to halt Shapur.

With Julian's reputation and exploits during his years as Caesar and general of Gaul preceding him, Shapur preferred to negotiate a peace treaty with the intrepid young Julian. Believing it to be incumbent on himself to produce a more permanent settlement in the East, Julian responded to Shapur's calls for peace by saying that the Persian king would be seeing him very soon and began preparing for an expedition against the Sassanid dynasty, collecting all his legions and marching east from Constantinople. Carefully planning and crafting his Persian campaign for over a year, Julian transferred his capital and forward base for the coming war to Antioch, Syria in the summer of 362 and on March 5, 363, set out with 90,000 men while Shapur, along with the main Persian army, spah, was away from Ctesiphon. Per his devised plan of attack, Julian sent 30,000 soldiers under the command of his maternal cousin Procopius to Armenia, with the aim of obtaining support from the King of Armenia for a clever and not looked-for double pincers movement against Shapur.

The battle
Seeing Julian successfully march into his dominions, Shapur ordered his governors to undertake a scorched earth policy until he reached the Sassanid capital, Ctesiphon, with the main Persian army. However after a few minor skirmishes and sieges Julian arrived with his undefeated army before Shapur II to the walls of Ctesiphon on May 29. Outside the walls a Persian army under Spahbod Merena was formed up for battle across the Tigris.

Julian's subordinate commanders were nervous, as the Persian army featured cataphracts in the centre and the formidable clibanarii on the wings. There were also war elephants and masses of infantry to the rear. However, Julian had already shown himself to be both a competent and confident general and did not share his subordinates’ worries. Instead, he drew up his army in a crescent formation, designed to achieve envelopment of Shapur's forces, and crossed the river to engage the enemy.

The wings of the Romans advanced swiftly and battle was joined. Contrary to expectations, the battle was a stunning tactical victory for the Romans, losing only 75 men to the Persians' 2,500 men. One of the Christian sources and not one friendly to the pagan Julian, Socrates Scholasticus, even states that Julian's victories up to this point in the campaign had been so great that they caused Shapur to offer Julian a large portion of the Persian domains if he and his legions would withdraw from Ctesiphon. But Julian rejected this offer out of desire for the glory of taking the Persian capital and defeating Shapur in battle which would earn him the honorific of Parthicus. However, Julian lacked the equipment to lay siege to the strongly fortified Ctesiphon, and the main Sassanid army, commanded by Shapur and far larger than the one just defeated, was closing in quickly. Also critical was the failure of Procopius to arrive with the 30,000 detachment of the Roman army that could have aided Julian in crushing Shapur's approaching force as he had intended. For as previously captured Satraps had testified after being fairly treated by Julian, the capture or death of Shapur would have compelled the Persian city to open its gates to the new Roman conqueror. While Julian was in favor of advancing further into Persian territory, he was overruled by his officers. Roman morale was low, disease was spreading, and there was very little forage around.

Death of Emperor Julian
Reluctantly, Julian agreed to retreat back along the Tigris and look for Procopius and the other half of his army that had failed to coordinate the double-pincers movement with him outside of Ctesiphon as had been planned. On June 16, 363, the retreat began and ten days later, outside Samarra, the army’s rearguard came under heavy attack. Not even pausing to put on his armour, Julian plunged into the fray shouting encouragement to his men. Just as the Persians were beginning to pull out with heavy losses, Julian was struck in the side by a flying spear. His liver fatally pierced, Julian died before midnight, on June 26, 363. Considered apocryphal is the report that his dying words were "Vicisti, Galilæe" ("Thou hast conquered, Galilean"), supposedly expressing his recognition that, with his death, Christianity would become the Empire's state religion.

Libanius in his orations commemorating the life and deeds of the last legitimate pagan Roman Emperor, initially stated that Julian was assassinated by a Christian who was one of his own soldiers, but later stated that the assassin was a Saracen, or Persian soldier. Ammianus Marcellinus, Julian's chief biographer and highly valued and praised historian of 354–378, also sheds doubt that a Christian was the guilty party and echoes Libanius' later thoughts that an unknown Persian committed the deed that cost Rome dearly. As a result, the truth of who killed Julian may never be known with certainty.

Aftermath
Julian was succeeded by the short-lived emperor Jovian, who lacked the martial vigor and strong will of his honored predecessor. As the Roman army was deep inside Sassanid territory, the inexperienced Jovian chose to make peace with Shapur, a peace received on unfavorable terms, in order to be allowed to safely lead his troops back to Roman territory. The humiliating peace terms required that the districts on the Tigris and Nisibis (a total of five Roman provinces) be ceded to the Persians, and the Romans promised to no longer interfere in the political affairs of Armenia. The death of Julian brought about the demise of formerly unchallenged Roman military supremacy in the East as the campaign of 363 would be the last great offensive campaign that consisted of legions and auxiliaries nearing 95,000 strong. Rome not only lost an effective and competent emperor and general in Julian, but its military policy after his death shifted permanently to a defensive posture.