Roman military diploma

A Roman military diploma was a document inscribed in bronze certifying that the holder was honourably discharged from the Roman armed forces and/or had received the grant of Roman citizenship from the emperor as reward for service.

The diploma was a notarised copy of an original constitutio (decree) issued by the emperor in Rome, listing by regiment (or unit) the eligible veterans. The constitutio, recorded on a large bronze plate, was lodged in the military archive at Rome (none such has been found; presumably they were melted down in later times).

Diplomas were issued during the Principate period (52-284 AD) to retiring veterans who had served in those corps of the Roman armed forces which enlisted peregrini, that is, inhabitants of the Roman empire who were not Roman citizens (the vast majority of the empire's population in the 1st and 2nd centuries). Such corps were: the auxilia; Roman navy, the Praetorian Guard's cavalry (equites singulares Augusti); and the cohortes urbanae (the City of Rome's public-order battalions).

The first known diploma dates from AD 52, under emperor Claudius (r. 41-54), who appears to have regularised the practice of granting Roman citizenship to non-citizen auxiliaries after 25 years' service (26 in the navy).

Diplomas were not normally issued to discharged legionaries, as the legions recruited Roman citizens only. However, legionary diplomas were exceptionally issued after the Civil War of 68/69 AD. As an emergency measure, 2 new legions, the I and II Classica (later reconstituted and renamed as I and II Adiutrix, respectively) were formed mainly from naval marines, many of whom did not hold citizenship. At the end of the crisis, these were all awarded Roman citizenship.

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