Legio IIII Martia: one of the legions of the later Roman empire. Its name indicates that the legionaries were especially dedicated to the war god Mars.
Coin of Aurelian
This legion is mentioned in the text known as Notitia Dignitatum, a catalogue of officials and commanders of Roman army units, as they existed in the late fourth century. This document states that the Fourth Martian legion was one of the units commanded by the general who was responsible for the protection of the province Arabia. This may not have been the most important of Rome's frontiers, but it was an arid zone, which made its defense rather difficult.
Lejjun, north gate
The legion was based in Betthorus, modern Lejjun (Jordan). It was already in existence when the emperor Diocletian (284-305) reorganized the oriental frontier. It may have been created by Aurelian (270-275), who sent western soldiers to the east after the annexation of the Palmyrene Empire.
The number four was the logical choice, because there was already a third legion (III Cyrenaica) in Arabia.
J. lander and S.T. Parker, "Legio IV Martia and the Legionary Camp at El-Lejjun", in: Byzantinische Forschungen 8 (1982) 185-210