Evocatus

Evocatus (plural Evocati) was the Latin term for a soldier in the Roman army who had served out his time and obtained a discharge (missio) but had voluntarily enlisted again at the invitation of the consul or other commander.

There always existed a considerable number of evocati in every army of importance, and when the general was a favorite among the soldiers, the number of veterans who joined his standard naturally increased. The evocati were officially released, like the vexillarii, from the common military duties of fortifying the camp, making roads, et cetera, and held a higher rank in the army than the common legionary soldiers. However their treatment was not guaranteed as some legionary commanders pressured men to stay on to ensure their command retained enough soldiers, as recruitment into the imperial legions was not a universally popular career choice.

They are sometimes written of in conjunction with the equites Romani, and sometimes classed with the centurions. They appear to have been frequently promoted to the rank of centurion and were customarily entitled to bear the vine staff and discipline fellow soldiers. Thus, Pompey induced a great many of the veterans who had served under him in former years to join his standard at the outbreak of the civil war with the promise of rewards and the command of centuries. Not all evocati could, however, have held the rank of centurion, nor could they belong to certain cohorts in the army. Cicero speaks of a Praefectus evocatorum, an officer in charge of the evocati.