In July of the year 335 Constantine celebrated his Tricennalia, i.e. his thirtieth year on the throne. The festivities in honour of this anniversary were obviously held in his new capital, Constantinople. Constantine was the Roman emperor with the longest reign since the great Augustus. It was not until the fifth century that considerably weaker emperors such as Honorius (395-423), Theodosius II (408-450) and Valentinianus III (425-455) got anywhere near Constantine’s number of years on the throne or – in the case of Theodosius – surpassed him. After his Tricennalia Constantine would live for almost two more years. During these years a conflict erupted with king Shapur II of Persia. In 299 the Roman Empire had made a highly favourable peace with the Sassanids. This peace had held for decades, but around 334 Shapur had invaded Armenia, which had its own king – Khosrov III – but was considered a Roman client state. Shapur was just 25 years old, but had been on the Persian throne since 309. This great-grandson of the great Shapur I (ca. 240-270) would soon become the most dangerous enemy that the Romans were faced with in the fourth century.
One big family
Constantine was in his early sixties when he celebrated his Tricennalia and must have realised that he did not possess eternal life. The big question was who would succeed him after his death. His eldest son Constantine (Constantinus) had been a caesar since 317 and was currently residing in Augusta Treverorum (Trier). Constantius, who was a year younger, had been appointed caesar in 324 and had taken up residence in Antioch in the east. In terms of economics and population this was the most important part of the Roman Empire. The third and youngest son, Constans, had not yet reached the age of manhood. His appointment as caesar dated from 333 and he had been sent to Mediolanum (Milan) so that in due time he could govern Italy and North Africa. And then there was Constantine’s nephew Dalmatius, whose age we do not know. As the son of Constantine’s half-brother Flavius Dalmatius he had been granted the title of caesar in 335. Dalmatius had settled in the Balkans and possibly had his residence at Naissus (Niš) or Sirmium (Sremska Mitrovica). All in all a division of the Roman Empire in four parts was beginning to take shape, but there was still just one augustus, Constantine himself.
Not only did Constantine refuse to discuss the matter of who would become the new augustus, in 336 he even complicated things a bit more. It was in that year that Dalmatius’ brother Hannibalianus married Constantine’s daughter Constantina. We do not know when Constantina was born, only that she died in 354 and that her mausoleum in Rome can still be visited. She may also have been responsible for the construction of a large funerary basilica in Rome, dedicated to Saint Agnes. Hannibalianus was not made a caesar, but was granted the title of “king” and even “king of kings” of Pontus and the surrounding areas. It is not entirely clear what Constantine wanted to achieve by creating this kingship, but the move was no doubt linked to the war against Shapur that the emperor was preparing.
The end of an era
The planned campaign against the Persians was ultimately never launched. In the spring of 337 Constantine, while on his way to Antioch, visited the town of Drepanon in Bithynia. Drepanon was where his mother Helena had been born, which is why Constantine had the town renamed Helenopolis. The emperor was very ill and felt that his last hour was approaching rapidly. He therefore summoned bishop Eusebius of Nicomedia, who baptised him on his deathbed. The first Christian emperor of the Roman Empire was now finally a proper Christian. An intriguing detail is that bishop Eusebius was, strictly speaking, a heretic, as he was a supporter of Arius’ doctrine on the nature of Christ. And this happened to be a doctrine that had been anathemised at the Council of Nicaea of 325, which had been summoned by Constantine. The fact that Constantine did not object to being baptised by an Arian bishop is perhaps the most compelling evidence that the emperor cared little about doctrinarian matters. On 22 May 337 Constantine passed away, about 65 years old, at an estate near Anchyrona, a village or town not far from Nicomedia. In spite of the many wars he had fought and the many murders, even of relatives, that had been committed on his orders, Constantine had certainly deserved his nickname “The Great”.
Constantine was buried in the church of the Holy Apostles in Constantinople, even though the edifice was not completed until after his death. It was Constantine’s middle son Constantius who led the funeral. The young man was about twenty years old and convincingly demonstrated why he was the apple of his father’s eye. As Constantine had not named his successor as augustus, the Roman Empire was now basically faced with an interregnum. Supported by the imperial bodyguard and the army, Constantine II, Constantius and Constans ultimately came out on top, and it is likely that the talented Constantius played a leading role in the process. Somewhere between the end of May and the beginning of September the soldiers eliminated Dalmatius and Hannibalianus. Their father Flavius Dalmatius and his brother Julius Constantius, both half-brothers of Constantine, were also killed. Other prominent victims of the purging of the court were the senators Flavius Optatus (consul in 334) and Ablabius (former praetorian prefect and consul in 331). Although the eldest son of Julius Constantius was also killed, his two younger sons Gallus and Julianus were spared. Gallus would later marry Constantina, while Julianus would marry Constantine’s other daughter Helena. In 361 he would even become augustus as Julianus ‘the Apostate’.
The interregnum ended on 9 September 337 when Constantine II, Constantius and Constans reached an agreement at Viminacium in the Balkans. The soldiers accepted the three brothers as their augusti, which meant that the Roman Empire now had three emperors. The division of the Empire largely corresponded with the division that had been in force when the brothers were still mere caesares. Constantius got the eastern provinces and Thrace, Constans the rest of the Balkans, North Africa and Italy, and Constantine II Gaul, Spain and Britannia. If after Viminacium the brothers had managed to work together in perfect harmony, they would no doubt have been able to continue the Golden Age initiated by their father Constantine. Unfortunately, all they did was plunge the Roman Empire into senseless and bloody civil wars within a few years.
- Anonymus Valesianus, Origo Constantini Imperatoris 35;
- Aurelius Victor, De Caesaribus 41 (translated and annotated by H.W. Bird);
- Epitome de Caesaribus 41;
- Eutropius, Breviarium Historiae Romanae 10.8-9;
- Zosimus, Historia Nova, Book 2.
- Henk Singor, Constantijn, p. 428-450;
- Timothy Venning, A Chronology of the Roman Empire, p. 661-662.
 Henk Singor, Constantijn, p. 444-445.
 Rex regum et Ponticarum gentium according to the Origo Constantini Imperatoris 6.35. The text on his coins is usually FL HANNIBALIANO REGI.
 Aurelius Victor, De Caesaribus 41. Victor writes that the emperor was “over 62 years old”. Timothy Venning, A Chronology of the Roman Empire, p. 661 gives his age as 61-63. Here I assume that Constantine was born in 272.
 Zosimus, Historia Nova, Book 2.40.
 Gallus was a son of Galla, Julianus of Basilina. The boys were therefore half-brothers.