User:LuciusHistoricus/Roman Persian Wars AD 337–363

The Roman–Persian Wars AD 337–363 were a series of conflicts between the Roman Empire and the Persian Sasanid Empire fought between 337 and 363. The main cause for the wars was Shapur II's attempts to recover the lands lost to the Romans by the Treaty of Nisibis.

The Persian Shah, Shapur II, had been conducting a policty of expansion ever since he went to war with the Arabs in 325. The Persians conquered the eastern parts of the Arabian peninsula; giving them control of the trade routes from India to the Roman Empire. This gave the Roman emperor, Constantine the Great, reasons to be concerned and, after finishing up his Danube campaigns, he stared preparing for a war in the East.

Constantine sent one of his sons, Constantius, as Caesar to the East to prepare the regional army for war. These preparations did not go unnoticed by the Persians. In 336, the Persian general Narses stormed Amida and marched into Roman Mesopotamia. Constantius marched out with the regional army and defeated an killed Narses at the Battle of Narasara. He then marched to Amida, reoccupied it, and rebuilt with new fortifications.

The Roman war plans failed when Constantine fell ill in April 337 and died on 22 May 337. Constantine's death plunged the Empire into a crisis of succession. Constantius had to abandon his campaign in Mesopotamia and returned to Constantinople, the Empire's new capital, to secure his claim to the throne. Eventually, Constantine's sons divided the Empire between themselves. Constantius, now as Constantius II, became emperor of the eastern part of the Empire, he ruled; Thrace, Asia Minor, Syria, Egypt, and Cyrenaica.

The First War: AD 337–350
Shapur's first major military opperation was a direct attack on the centre of Roman Mesopotamia: Nisibis. The offensive was probably not pre-planned, but a result of the opportunities offered by the death of Constantine. Shapur marched his vast army composed of cavalry, infantry and elephants against the Roman-held city. His combat engineers raised siege works, including towers, so his archers could rain down arrows at the defenders. They also undermined the walls, dammed the Mygdonius River and constructed dikes to direct the river against the walls. On the seventieth day of the siege, the water was released and the torrent struck the walls; entire sections of the city walls collapsed. The water passed through the city and knocked down a section of the opposite wall as well. The Persians were unable to assault the city because the approaches to the breaches were impassable due to floodwater, mud and desbris. The soldiers and citizens inside the city worked all night and by dawn the breaches were closed with makeshift barriers. Shapur's assault troops attacked the breaches, but their assault was repulsed. A few days later the Persian lifted the siege.

With the death of Constantine, his Praesental Army (his Field Army) was divided among his sons. This meant Constantius had only one-third of the Empire's Comitatenses at his disposal. He also only had one-third of the rest of the Empire's resources at his disposal which prevented large scale opperations. Despite this Constantius took the field in 338 and reinstalled a Roman nominee on the Armenian throne. Shapur's losses during the siege must have been high, or he must have been occupied on his eastern borders, because he declined a general engagement between 338 and 343.

In 344, Shapur invaded Roman Mesopotamia again and attacked the city of Singara. Constantius, in response, marched his army to Singara to confront the Persians and force them into a decisive battle. Shapur decided to give battle and formed his heavy infantry and heavy cavalry in front of his battlements. He then sent his light cavalry to the Roman camp to attack Constantius and lure him in. The Romans observed a large body of enemies approaching their camp and Constantius marched out his army into battle formation. The engagement started with the Persian and Roman cavalry and light infantry skirmishing using bows, slings, javelins and darts. As the Romans advanced the Persians kept falling back towards their camp. After hours of fighting in the heat of the day the Roman battle line arrived at the Persian camp. This is when Shapur sent in his fresh heavy troops. Unfortunately for the Persians, the fresh troops were stopped by Roman light infantry armed with clubs. With the unexpected defeat of their heavy troops the Persians broke and fled back to their camp. During the confused fighting that followed Shapur's son was killed. As night fell the Romans broke into the Persian camp and started looting and searching for water. Meanwhile, Shapur had rallied his troops east of the camp and he sent out his archers to take position on the hills around the camp. The Romans were illuminated by the burning camp and many were crowded around the cisterns quenching their thirst. They became easy targets for the Persian archers who caused heavy casualties on the disordered Romans. Constantius broke of his pursuit of the Persians and Shapur withdrew his army across the Tigris. The Battle of Singara was technically a Roman victory because they held the field of battle and took the Persian camp, but Roman casualties made it a Pyrrhic Victory at best.