First Mesopotamian campaign of Ardashir I

Between 224 and 226/227, an important episode changed the fate of relations between the Roman and Persian empires: in the East, the last Parthian ruler, Artabanus IV, was overthrown after being defeated in "three battles," and the insurgent, Ardashir I, founded the Sasanian dynasty, destined to be the eastern adversary of the Romans until the 7th century. Specifically, beginning in 229/230, Sasanians and Romans clashed for the first time. On the Roman front, the new Severan dynasty that reigned over the Roman Empire between the end of the second and the first decades of the third century (from 193 to 235, with a brief interruption during the reign of Macrinus between 217 and 218), and which had had in Septimius Severus its progenitor, was now in the hands of a young emperor, Severus Alexander, who a few years later was killed, revealing himself to be the last descendant. The new dynasty had arisen on the ashes of a long period of civil wars, where three other contenders besides Septimius Severus (Didius Julianus, Pescennius Niger, and Clodius Albinus) had faced each other. Casus belli The casus belli was the claim by the Sasanian Empire, who considered themselves descendants of the Persians, to possession of the entire Achaemenid Empire, including the territories, now Roman, of Asia Minor and the Near East as far as the Aegean Sea. == Forces in the field ==

Sasanian Empire It is not known precisely how many and what armies were fielded by the Sasanian Empire. Cassius Dio recounts that it was certainly a large army, ready to terrorize not only the Roman province of Mesopotamia but also that of Syria, west of the Euphrates. Rather, the system was similar to the feudal one, where for each campaign it was necessary to assemble an army from time to time, composed of nobles at the head of their "clans," subjected then under the command of a prince of the royal house. Thus, there were no experienced weapons officers serving continuously, nor was there a lasting system of recruitment, as there were no permanent military units, although there were many nobles at the disposal of the Sasanian army. For these reasons, they often hired mercenary armies. However, unlike the Arsacid Parthians, they tried to keep their contingents under arms for more years during major military campaigns, speeding up the recruitment of their armies, as well as better assimilating the siege techniques of their Roman opponents, which they never really learned from their predecessors. Roman Empire It is known that for the Romans, the forces put in charge were represented by the legions and auxiliary troops stationed along the eastern lines, which, according to Cassius Dio, were not enough prepared in terms of discipline and morale to cope with this new eastern danger. Below is a list of the legions and their respective fortresses (to which one might later add the IV Italica, formed around 231 by Severus Alexander): == Stages of the conflict ==

First phase: Sasanian advance in Mesopotamia (229-231) 229 ca. With the rise of the first Sasanian ruler, Ardashir I, the Persian armies returned to unsuccessfully besiege the city of Hatra (to make it a base of attack against the Romans.) It is not known whether it was under direct Roman control, or simply a "client" city of the Roman Empire. After the failure of this siege, the Sasanian ruler went first to Media, 230 In the course of this year, the Sasanian armies advanced into Roman Mesopotamia laying siege to many Roman garrisons along the Euphrates, also attempting, unsuccessfully, to conquer Nisibis (an important center of trade with the East and China), and perhaps invading the Roman provinces of Syria and Cappadocia, although there is insufficient archaeological evidence, at least in the present state of knowledge, to say that the raids also affected territories west of the Euphrates. 231 Emperor Severus Alexander then organized a new military expedition against the Sasanians, enlisting a new legion in Italy, Legio IIII Italica. to reach his headquarters in Antioch. However, the campaign proved not entirely bad for the Romans, as the territories lost in Mesopotamia in the course of the Sasanian advance of 229-230 were recaptured and the Sasanians did not renew their assaults until around 237, but this time, they were much more successful. Alexander took the victorious titles of Parthicus maximus and Persicus. == Consequences ==

The death of the young emperor at the hands of one of his generals, Maximinus the Thracian (in 235), and the subsequent military anarchy into which the Roman Empire poured for about fifty years, determined considerable advantages in favor of the nascent Sasanian Empire, which did not miss the opportunity to go so far as to occupy Antioch itself in 252 and 260. == See also ==