The Frumentarii – Rome’s army of spies

The Frumentarii were a branch attached to the Roman military, whose purpose has been the subject of much speculation.

Frumentarii is the Latin word for grain (frumentum), leading to the interpretation that the Frumentarii were merely grain collectors involved in the military commissariat.

This is based on text by Aulus Hirtius, a politician and writer during the 1st century BC, who referred to soldiers engaged in transporting grain as Frumentarii, found in the 8th book of Caesar’s De Bello Gallico.


Further evidence can be found in an Ostian inscription from AD 210, which shows a centurio frumentarius erecting a dedication to Praefectus Annonae, the official in charge of Rome’s grain supply.

Supplying grain for the army was an important role in itself, however, historians have proposed that their duties extended over time into a secret police force of spies, couriers, assassins, and an intelligence agency for the Roman Empire sometime during the late 1st or 2nd century AD.

It is possible that the Frumentarii inherited these duties from the Speculatores, also known as the Speculatores Augusti or the Exploratores, who were a Roman reconnaissance agency first mentioned in the Samnite Wars and the Roman war with the Aequi.

Any mention of the Frumentarii serving as military police is lacking in the literary sources and instead mainly appears in epigraphic evidence. Inscriptions found in Anatolia describe them arresting villagers and confiscating their belongings, while inscriptions in Italy, Raetia and Egypt note them serving as a military guard at important sites such as mines.


While still maintaining the role of grain supply agents, this would bring them into close contact with governors, commanders of the army, and important officials. This gave them unprecedented access, so it was a relationship of convenience that they also served as couriers and assassins.

It was not uncommon for these couriers to commit espionage services, where emperors would use them to gather information on friends, family and officials. An example of this can be found in the Historia Augusta, a late Roman collection of biographies of the Roman emperors.

In the biography on the life of Hadrian, the Historia Augusta describes: “[Hadrian’s] vigilance was not confined to his own household but extended to those of his friends, and by means of his private agents (frumentarios) he even pried into all their secrets, and so skilfully that they were never aware that the Emperor was acquainted with their private lives until he revealed it himself.”

The Frumentarii were abolished during the reign of Diocletian (reigned AD 284 to 305) when a reorganisation of the taxation system and a preference for a civilian infrastructure made them redundant.

It has also been argued that their abolishment was the result of their disfavour among the Roman people, for false and arbitrary arrests, killings and an abuse of their position.

As part of Diocletian’s reforms, a new courier unit called the “agentes in rebus” was created, serving as the official Roman imperial courier service and general agents of the central government.

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Markus Milligan
Markus Milligan
Markus Milligan - Markus is a journalist and the Managing Editor at HeritageDaily. His background is in archaeology and computer science, having written over 7,000 articles across several online publications. Markus is a member of the Association of British Science Writers (ABSW).



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