Legatus

A legatus (anglicised as legate) 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. In order to command an army independently of the dux or provincial governor, legates were required to be of praetorian rank or higher; a legate could be invested with propraetorian imperium (legatus pro praetore) in his own right. Legates received large shares of the army's booty at the end of a successful campaign, which made the position a lucrative one, so it could often attract even distinguished consuls (e.g., the consul Lucius Julius Caesar volunteered late in the Gallic Wars as a legate under his first cousin once removed, Gaius Julius Caesar).

The men who filled the office of legate were drawn from among the senatorial class of Rome. There were two main positions; the legatus legionis was an ex-praetor given command of one of Rome's elite legions, while the legatus pro praetore was an ex-consul, who was given the governorship of a Roman province with the magisterial powers of a praetor, which in some cases gave him command of four or more legions. Due to his advanced senatorial status, a legatus was entitled to five fasces and five lictors.

This rank was also the overall legionary commander. This post was generally appointed by the emperor. The person chosen for this rank was a former tribune, and although the emperor Augustus set a maximum term of command of two years for a legatus, subsequent emperors extended the tenure to three or four years, although he could serve for a much longer period. In a province with only one legion, the legatus was also the provincial governor, but in provinces with multiple legions, each legion had a legatus and the provincial governor (who was separate from the legions) had overall command.

The legatus could be distinguished in the field by his his elaborate helmet and body armour, as well as his scarlet paludamentum and cincticulus. The latter was a scarlet waist-band tied around his waist in a bow.

Diplomatic legatus
Legatus was also a term for an ambassador of the Roman Republic who was appointed by the senate for a mission (legatio) to a foreign nation, as well as for ambassadors who came to Rome from other countries. This is the sense of the word that survives in the phrase Papal legate.