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.
Severus' War Against Parthia
[3.9.1]  Severus now remained in Rome for a long time, during which his sons were partners with him in governing the empire.note[Caracalla had already been made caesar in 196, and Severus - on his return from the campaign against Albinus - immediately proceeded to Syria to continue the war against the Parthians that had began in 194.] He was then seized with a desire to win glory for victories not only over fellow countrymen and Roman armies but also barbarians; using as an excuse for his action the friendship shown to Niger by Barsemius, king of the Hatrenians, he led his army off to the East.
[3.9.2] When he arrived there his intention was to invade Armenia also. But the king of the Armenians forestalled him by sending money, gifts, and hostages to support his plea for peace and by promising pacts and good will. After affairs in Armenia had thus turned out to his satisfaction, Severus marched against the Hatrenian kingdom. At this time Abgarus, the Osrhoenian king,note[Another name for this kingdom is Edessa. The description of this war appears to be based on a misinterpretation of the reliefs of the Arch of Septimius Severus.] fled to Severus and gave him his children as a guaranty of his support; he also brought a great number of archers to fight in the Roman army.
[3.9.3] After passing through the region between the Tigris and Euphrates rivers and the country of the Adiabenes,note[Their capitals were Arbela and Nisibis.] Severus hurried on into Arabia Felix,note[An error. Severus campaigned in a zone where Arabs lived. Arabia Felix is modern Yemen.] the country which produces the fragrant plants we use in our perfumes and incense. When he had destroyed many towns and villages there and had plundered the countryside, he came into the territory of the Hatrenians, where he encamped and laid siege to the city of Hatra.
[3.9.4] This city, located on top of a lofty mountain, was surrounded by a high, strong wall manned by many bowmen. After making camp, Severus' soldiers pressed the siege with all the power at their command, endeavoring to capture the city. Engines of every type were brought up to the wall, and all the known tactics were tried.
[3.9.5] The Hatrenians fought back bravely; pouring down a steady stream of stones and arrows, they did considerable damage to the army of Severus. Making clay pots, they filled them with winged insects, little poisonous flying creatures. When these were hurled down on the besiegers, the insects fell into the Romans' eyes and on all the unprotected parts of their bodies; digging in before they were noticed, they bit and stung the soldiers.
[3.9.6] The Romans found the air at Hatra intolerable, stifling from the hot sun; they fell sick and died, and more casualties resulted from disease than from enemy action.
[3.9.7] When the army, for the reasons mentioned above, had abandoned all hope and the siege was at a stalemate, with the Romans losing instead of gaining ground, Severus led his troops away unsuccessful, fearing that he would lose his entire army. The soldiers were unhappy that the siege had not turned out as successfully as they wished;
[3.9.8] accustomed to victory in all their battles, they believed that failure to win was actually defeat. But Fortune, by furthering his affairs at this time, provided Severus a measure of consolation; he did not return home without some success, and the truth is that he accomplished more than he had expected.
[3.9.9] The army, sailing in a large number of ships, was not borne to its intended destination on Roman-held shores, but after the current had carried the fleet a great distance, the legions disembarked on Parthian beaches at a spot within a few days' march of the road leading to Ctesiphon, where the royal palace of the Parthians was located. There the king was spending his time peacefully, thinking that the battles between Severus and the Hatrenians were no concern of his.
[3.9.10] But the troops of the emperor, brought by the current to these shores against their will, landed and plundered the region, driving off for food all the cattle they found and burning all the villages as they passed. After proceeding a short distance, they stood at the gates of Ctesiphon, the capital city of the great king Artabanus.note[The king was in fact named Vologasus V.]
[3.9.11] [28 January 198] The Romans fell upon the unsuspecting barbarians, killing all who opposed them. Taking captive the women and children, they looted the entire city. After the king fled with a few horsemen, the Romans plundered the treasuries, seized the ornaments and jewels, and marched off.
[3.9.12] Thus, more by luck than good judgment, Severus won the glory of a Parthian victory. And since these affairs turned out more successfully than he had any reason to hope, he sent dispatches to the senate and the people, extolling his exploits, and he had paintings of his battles and victories put on public display. The Senate voted him the titles formed from the names of the conquered nations, as well as all the rest of the usual honors.