Last updated: 27 December 2017

Illustrated with exemplar coins

Diocletian's Tetrarchic system of Governance

[Diocletian coin photo]
The Dyarchy: Diocletian & Maximian Herculius (follis coin portraits)

Diocletian (Caius Aurelius Verus Diocletianus) was proclaimed Augustus in AD 284. The following year he appointed Marcus Aurelius Valerius Maximianus (Maximian Herculius), a close military comrade, as his Caesar elevating him to co-Augustus a year later thereby creating a Dyarchy.

In 293 Diocletian finalized the Institution of a Tetrarchy -- government of the Empire by four interacting rulers -- two Augusti assisted by two subordinate Caesars, which each Augustus would personally select. The two Caesars, chosen because of their proven leadership abilities, assisted the Augusti with civil administration and command of the armies. Caius Galerius Valerius Maximianus (Galerius Maximian) was chosen by Diocletian to be his Caesar of the East and Flavius Valerius Constantius (Constantius) was chosen by Maximian Herculius be his Caesar of the West. The Empire was divided into four geographical areas of governance: Diocletian and Galerius Maximian maintained their eastern headquarters at Nicomedia and Thessalonica respectively, while Maximian Herculius and Constantius maintained their western headquarters at Milan and Trier respectively.

Problems with Roman occupied Britain and the emergence of Carausius

The political and military turmoil of the third century spawned numerous external assaults on the Roman Empire. One of these was the incessant seafaring piracy in the waters surrounding the Roman occupied island outpost of Britain. In 286 Maximian Herculius, in his capacity as Dyarch Augustus of the West, designated a highly regarded military commander named Marcus Aurelius Mausaeus Carausius, of Flemish descent, to head a fleet of ships who's mission was to eliminate, or at least severely curtail, this piracy. Carausius had distinguished himself by outstanding leadership and military prowess, especially as a naval "Admiral", in the Gallic campaigns. Carausius established his operational base at the coastal city of Boulogne (Gesoriacum) in Roman occupied northern Gaul. Carausius did indeed accomplish his mission, but reports of corruption and extortion led Maximian Herculius to dispatch a fleet of ships in order to remove Carausius from command. However, Carausius proved too strong and he repulsed the attack.

Carausius - Usurper Augustus of Secessionist Britain

RIC V (2), Carausius, Antoninianus, No. 475:

IMP C CARAVSIVS PF AVG ......................................... PA - X - AVG | S .....P

Carausius subsequently used his continental base to launch an invasion force to occupy and subjugate Britain. Landing in the north, Carausius secured the support of the native Picts and, advancing south, confronted and defeated the forces of the Roman Governor. Having thus conquered the Island, he proclaimed himself Augustus of a Secessionist Britain, becoming an effective and efficient Administrator using the Roman Imperial governmental framework as a model. He maintained control of Boulogne and coastal northern Gaul.

Allectus Chief Minister of Carausius - and who was his Assassin

RIC V (2), Allectus, Antoninianus, No. 33:

IMP C ALLECTVS P F AVG ............................. PA - X - AVG ..... S (Pax standing left) A
M L in reverse exergue.

In AD 293, Allectus, the chief minister of Carausius, assassinated him (or orchestrated his assassination) and proclaimed himself Augustus of Secessionist Britain.

Constantius prepares for the Invasion of secessionist Britain

The first assignment given Constantius by Maximian Herculius was to restore that former possession to the Empire. Constantius thereupon besieged and captured Boulogne and then wrested coastal Gaul from Carausius. Constantius now set about planning the invasion, occupation and restoration of Secessionist Britain to the Empire. One of the first orders of business for Constantius in 294 was to insure that a supply of reformed aes coinage (folles) - now the commonplace legal tender of the Roman Empire - was available for use not only by his occupying force, but also by the British civilian populace. To that end Constantius established a Mint in Gaul (exact location usually listed as unknown, although some French sources list it as Boulogne), manned by Lugdunese mint workers, to produce this invasion coinage - unmarked (i.e. without a mint mark) issued in the names of Diocletian & Maximian Herculius as Augusti and Constantius & Galerius Maximian as Caesars.

RIC Volume VI, Lugdunum, No. 17a, Constantius, Caesar of the West:

[Constantius coin photo][Constantius coin photo]
FL VAL CONSTANTIVS NOB C .............................. GENIO POPV -- LI ROMANI

Restoration of Secessionist Britain to the Empire by Constantius

In 296 Constantius launched a powerful naval invasion force against Britain in two divisions: one led by himself, which sailed from Boulogne and the other led by the Praetorian Prefect of Maximian Herculius, Asclepiodotus, which sailed from the mouth of the river Seine. The mission of Constantius was to remove Allectus from power and restore Britain to the Empire. This mission was accomplished and although Constantius was in overall command of the operation, some historical sources assert it was the force under Asclepiodotus that did most of the fighting on land and in fact it was they who defeated and killed Allectus during the decisive battle. Constantius subsequently entered the city of London to proclaim his conquest as restorer of the eternal light of the Roman Empire: Redditor Lucis Aeternae.

The following photograph of a bronze copy of the famous ten aurei multiple (RIC VOLUME VI, TREVERI, No. 34), the original of which presently resides in the museum at Arras, commemorates the restoration of Britain to the Roman Empire by Constantius in 296. It depicts the personification of Londinium (LON) kneeling and supplicating to Constantius (on horseback) outside of the City Fortification while a galley with Roman soldiers waits on the river Thames(?).

[Constantius medallion photo][Constantius medallion photo]
LON (reverse right) PTR (reverse exergue)

Constantius re-opens the Carausius/Allectus London Mint

Constantius re-opened the London Mint, now as an official facility with one officina (workshop), which continued to operate, somewhat sporadically, until its closure in 325. It seems very likely that initially the work force consisted of British die engravers and other workers, formerly employed by the Carausius/Allectus Mints, now supervised and mixed in with Lugdunese mint workers who accompanied the Constantius invasion force.

This London Mint continued to produce exclusively reformed folles, first under Constantius and then under Constantine, until its closure in AD 325.

RIC Volume VI, Londinium, No.1a, Diocletian, Augustus of the East:

[Diocletian coin photo][Diocletian coin photo]
in reverse exergue

Intermediate series coin (Bastien), not in RIC, Galerius Maximian, Caesar of the East:

[Galerius coin photo][Galerius coin photo]
C VAL MAXIMIANVS NOB C ........................... GENIO POPV -- LI ROMANI

RIC VI, Londinium, No.6b, Maximian Herculius, Augustus of the West:


Diocletian plans his Abdication - and includes a reluctant Maximian Herculius

It seems Diocletian had always envisioned that there would come a time when he (along with his co-Augustus) would have to relinquish the reins of supreme power and retire (for whatever reason). He chose the occasion of his Vicennalia -- the twentieth anniversary of his assumption of power as Augustus and coincidentally the tenth anniversary (Decinnelia) of his institution of the Tetrarchy -- to Abdicate and retire and persuaded (compelled?) Maximian Herculius to do the same in concert with him. And so, in 303 the two Augusti announced their intention to simultaneously abdicate and retire (Maximian Herculius somewhat reluctantly) in 305, their titles and authority to be assumed by the Caesars, who in turn would appoint new Caesars thus perpetuating the system. This was, of course, the only instance of an Abdication during the Tetrarchy -- it didn't survive as an institution long enough to witness another one. Although Diocletian had provided a model for perpetuation of the system attending an Abdication, he didn't provide one to follow in the event of the sudden death of one, or both, of the reigning Augusti, and that had dire consequences for the Tetrarchy when Constantius (Augustus of the West) died suddenly in 306.

Severe illness of Diocletian

In 304 Diocletian became very ill (unknown cause - possibly a stroke) that resulted in a lengthy convalescense and withdrawal from public life.

Abdication of Diocletian and Maximian Herculius

On 1 May 305, Diocletian and Maximian Herculius abdicated to become Seniore (retired) Augusti.

RIC VI, Londinium, No. 76b, Maximian Herculius, retired senior Augustus:

[Abdication coin photo][Abdication coin photo]

The successor Tetrarchs

On 1 May 305, Constantius succeeded Maximian Herculius as Augustus of the West and Galerius Maximian succeeded Diocletian as Augustus of the East. Flavius Valerius Severus (Severus), a close friend of Galerius Maximian, was appointed Caesar of the West by Constantius and Galerius Valerius Maximinus Daia (Maximinus Daza) was appointed Caesar of the East by Galerius Maximian.

RIC VI, Londinium, No. 47, Constantius, Augustus of the West:

[Constantius coin photo][Constantius coin photo]

RIC VI, Londinium, No. 42, Galerius Maximian, Augustus of the East:

[Galerius coin photo][Galerius coin photo]
IMP C MAXIMIANVS P F AVG ......................... GENIO POPV -- LI ROMANI

RIC VI, Londinium, No. 63a, Severus, Caesar of the West:

[Severus coin photo][Severus coin photo]
SEVERVS NOBILIS C ........................................ GENIO POPV -- LI ROMANI

RIC VI, Londinium, No. 65, Maximinus (Daia), Caesar of the East:

[Maximinus coin photo][Maximinus coin photo]

The death of Constantius

Constantius died at Eboracum (York) in Britain during a campaign against the warlike tribes of the North on 25 July 306. Just before he died, Constantius conferred Imperium on his son, Flavius Valerius Constantinus (later Constantine the Great). The army commanded by Constantius wanted Constantine proclaimed Augustus to succeed his father, however, Galerius Maximian, the now de-facto senior Augustus elevated Severus to Augustus of the West and affirmed Constantine as Caesar (of the West?).

Author note: I believe that the Tetrarchy began to fall apart at this point in time. Surely Severus should automatically have assumed the title of Augustus of the West and then selected his own Caesar in accordance with precedent. Of course, Constantius conferring Imperium on his son and Galerius Maximian subsequently affirming him as Caesar threw a monkey wrench in the works and Galerius Maximian was stuck with the task of sorting it all out.

RIC VI, Londinium, No. 46 (variant), Severus, Augustus of the West:

IMP SEVERVS PIVS FEL AVG ........................... GENIO POPV - LI ROMANI

RIC VI, Londinium, No. 89b, Constantine, Caesar of the West (?):

[Constantine coin photo][Constantine coin photo]
FL VAL CONSTANTINIVS NOB C ........................... GENIO - POP ROM
in reverse exergue

Revolt in Rome - Maxentius is "proclaimed" Augustus

On 28 October 306, the Citizens of Rome revolted against oppressive taxation and petitioned Marcus Aurelius Valerius Maxentius (Maxentius), son of retired Augustus Maximian Herculius, to assume Imperium. This he did, initially adopting the appellation of Princeps although his army proclaimed him Augustus.

Maximian Herculius as "colleague Augustus" of his son, Maxentius

Maxentius persuaded his father, Maximian Herculius, to come out of retirement in order to serve as his "colleague Augustus".

RIC VI, Ostia, No. 35, Maxentius as Augustus:

[Maxentius coin photo][Maxentius coin photo]
IMP C MAXENTIVS PF AVG .................................. AETERNITAS AVG N
in reverse exergue

RIC VI, Londinium, No. 85/90, Maximian Herculius as Augustus emerged from retirement:

[Licinius coin photo][Licinius coin photo]
DN MAXIMINIANO PFS AVG ................................... GENIO POP ROM
in reverse exergue

Severus sets out to depose Maxentius but is defeated and executed

Galerius Maximian, the de-facto senior Augustus, rejected the actions of Maxentius as illegal and instructed Severus (because Rome was in his sphere of authority) to engage Maxentius and depose him. Early in 307 Severus commanded an army that marched south into Italy to engage Maxentius as instructed by Galerius Maximian. Severus was not well served by this army that maintained loyalties to its previous commander, Maximian Herculius, and indeed many soldiers deserted Severus. The forces of Maxentius quickly defeated those of Severus who was captured and subsequently executed in Rome. Maximian Herculius thereupon set about organizing the defense of Rome against an anticipated attack by Galerius Maximian and in April traveled to Gaul seeking an alliance with Constantine, Caesar of the West, in order to strengthen his position. The alliance was duly consummated and cemented when Constantine married the daughter of Maximian Herculius, Fausta Flavia Maxima (Fausta). Constantine assumed the title and powers of Augustus later in the year (not recognized by Galerius Maximian) after personal affirmation(?) by Maximian Herculius. There was now a legitimately appointed Augustus - Galerius Maximian, one dubiously assumptive Augustus - Maximian Herculius, and two very questionably appointed Augusti - Constantine and Maxentius. The structure of the Tetrarchy was now in shambles.

The Conference at Carnuntum - attempting to restore the Tetrarchy

In the spring of 308 Maximian Herculius had a falling out with his son, Maxentius, and left to join his now son-in-law, Constantine, in Gaul. In the autumn of 308 Galerius Maximian organized and convened a conference at Carnuntum consisting of himself, Diocletian and Maximian Herculius (as retired seniore Augusti) to discuss and resolve the "Augusti problem". Diocletian was but a shadow of his former self, both mentally and physically, due to the severe illness that befell him in 304 and consequently Galerius Maximian "ran the show" -- he was now the dominant force in the Tetrarchy. Galerius Maximian did not recognize either Constantine or Maxentius as Augustus, proposing instead that his old friend and military comrade Flavius Valerius Licinianus Licinius (Licinius), be appointed Augustus of the West to replace the deceased Severus and he obtained the concurrence of Diocletian and Maximian Herculius in this maneuver. Maxentius was declared an enemy of the state by the conferees and Maximian Herculius once more went into retirement. Galerius Maximian proposed that Constantine be recognized as Caesar of the West, although Constantine did not acquiesce.

Constantine was incensed at his proposed "demotion" to Caesar subservient to Licinius as was Maximinus at the elevation of Licinius to Augustus over him, and so Galerius Maximian designated both of them Filius Augustorum: "son of the Augustus" -- a somewhat empty title of convenience and compromise -- in an attempt to mollify them.

RIC VI, Thessalonica, No. 32a, Maximinus Daia as Filius Augustorum:

[Licinius coin photo][Licinius coin photo]
MAXIMINVS FIL AVGG ................................... GENIO CAESARIS
in reverse exergue

Imperial claimants - death of Maximian Herculius & Galerius Maximian

There now followed a struggle between the Imperial Claimants: Maximian Herculius, who had again emerged from retirement as a self-proclaimed Augustus, and evidently with intentions to usurp Constantine, was defeated in battle by Constantine in 309 and committed suicide in 310 after betrayal by his daughter, Fausta, (wife of Constantine). Maximinus was proclaimed Augustus by the troops of his army in the same year.

Galerius Maximian, the last surviving original Tetrarch and reigning senior Augustus, was afflicted with a fatal urinary/reproductive tract disease in 308 and died a painful, lingering, death on 5 May 311.

Maximinus and Maxentius formed a Military Compact early in 312 but Maxentius was defeated and killed by the forces of Constantine during a famous battle at Milvian bridge outside Rome later that year. The forces of Maximinus were defeated by those of Licinius in 313, Maximinus committing suicide later that year. Constantine and Licinius were subsequently proclaimed co-Augusti, bringing down the curtain on this Historical Period.

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