Herodian (late second, first half third century): Greek historian, author of a History of the Roman Empire since the Death of Marcus Aurelius in which he describes the reign of Commodus (180-192), the Year of the Five Emperors (193), the age of the Severan dynasty (211-235), and the Year of the Six Emperors (238).
The translation was made by Edward C. Echols (Herodian of Antioch's History of the Roman Empire, 1961 Berkeley and Los Angeles) and was put online for the first time by Roger Pearse (Tertullian.Org). The version offered on these pages is hyperlinked and contains notes by Jona Lendering.
End of the Persian War
[6.6.1]  When the disaster was reported to Alexander, who was seriously ill either from despondency or the unfamiliar air, he fell into despair. The rest of the army angrily denounced the emperor because the invading army had been destroyed as a result of his failure to carry out the plans faithfully agreed upon.
[6.6.2] And now Alexander refused to endure his indisposition and the stifling air any longer. The entire army was sick and the troops from Illyricum especially were seriously ill and dying, being accustomed to moist, cool air and to more food than they were being issued. Eager to set out for Antioch, Alexander ordered the army in Media to proceed to that city.
[6.6.3] [Winter 232/233] This army, in its advance, was almost totally destroyed in the mountains [of Armenia]; a great many soldiers suffered mutilation in the frigid country, and only a handful of the large number of troops who started the march managed to reach Antioch. The emperor led his own large force to that city, and many of them perished too; so the affair brought the greatest discontent to the army and the greatest dishonor to Alexander, who was betrayed by bad luck and bad judgment. Of the three armies into which he had divided his total force, the greater part was lost by various misfortunes - disease, war, and cold.
[6.6.4] In Antioch, Alexander was quickly revived by the cool air and good water of that city after the acrid drought in Mesopotamia, and the soldiers too recovered there. The emperor tried to console them for their sufferings by a lavish distribution of money, in the belief that this was the only way he could regain their good will. He assembled an army and prepared to march against the Persians again if they should give trouble and not remain quiet.
[6.6.5] But it was reported that Artaxerxes had disbanded his army and sent each soldier back to his own country. Though the barbarians seemed to have conquered because of their superior strength, they were exhausted by the numerous skirmishes in Media and by the battle in Parthia,note[Not the real Parthia in northeastern Iran, but the parts east of the Euphrates.] where they lost many killed and many wounded. The Romans were not defeated because they were cowards; indeed, they did the enemy much damage and lost only because they were outnumbered.
[6.6.6] Since the total number of troops which fell on both sides was virtually identical, the surviving barbarians appeared to have won, but by superior numbers, not by superior power. It is no little proof of how much the barbarians suffered that for three or four years after this they remained quiet and did not take up arms. All this the emperor learned while he was at Antioch. Relieved of anxiety about the war, he grew more cheerful and less apprehensive and devoted himself to enjoying the pleasures which the city offered.