The vir militaris was a Roman

Roman army

The Roman army is the generic term for the terrestrial armed forces deployed by the kingdom of Rome , the Roman Republic , the Roman Empire and its successor, the Byzantine empire...

 legate

Legatus

A legatus was a general in the Roman army, equivalent to a modern general officer. Being of senatorial rank, his immediate superior was the dux, and he outranked all military tribunes...

 (or general) that governed a consular military province of the Roman Empire

Roman Empire

The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

. Tacitus

Tacitus

Publius Cornelius Tacitus was a senator and a historian of the Roman Empire. The surviving portions of his two major works—the Annals and the Histories—examine the reigns of the Roman Emperors Tiberius, Claudius, Nero and those who reigned in the Year of the Four Emperors...

mentioned the phrase vir militaris in some of his passages in order to describe ordinary soldiers or junior officers. Overall, the name was given to anyone who was experienced in military life or was given an opportunity to establish a reputation through warfare. According to Brian Campbell, the viri militares did not represent a homogeneous unit with special characteristics.

Source

• Campbell, Brian. "Who Were the Viri Militares?" The Journal of Roman Studies. Vol. 65, pp. 11-31, 1975.