Eutropius Early Years:
There appear to have been at least two men named Eutropius who lived around the same time. We know little for certain about either. One Eutropius is named as a government official in legal codes and the letters of Symmachus and Libanius without mention of his being an historian.
David Rohrbacher assumes this man was the historian. Eutropius may have been born around A.D. 320. This date gives him a decade of civil service work prior to reaching the position of magister epistularum before 361.
Work As "Magister Epistularum" Under the Roman Emperors:
As magister epistularum, Eutropius dealt with the transfer of judicial, military, and civil service-related paperwork from both sides of the Empire. Eutropius served in this capacity under Constantius and then continued under Julian.
Promotion of Eutropius Under Valens:
Under the Emperor Valens, Eutropius may have been promoted to magister memoriae between 367 and 369. In this capacity, he wrote his Breviarium. In 371, a Eutropius was proconsul in Asia. The magister memoriae who followed Eutropius, Festus, became proconsul in Asia after him.
Festus accused Eutropius of complicity in a plot against Emperor Valens. Ammianus says this was a false accusation. Tortured testimony did not corroborate Festus' accusation, so Eutropius escaped execution.
In "Eutropius V. C. 'Magister Memoriae?'" R. W. Burgess, Classical Philology, Vol. 96, No. 1. (Jan., 2001), pp. 76-81, Burgess speculates about the significance of Festus and Eutropius each writing a Breviarium at the same time (369-70). Burgess suggests that only one of them could have been magister memoriae but that both Festus and Eutropius were asked simultaneously to write Brevaria. He suggests each man was given a different focus.
Eutropius Under Gratian, Theodosius, and Valentinian II:
This same Eutropius may have been appointed prefect of Illyricum where in 380 and 381 laws were written under his name. In 387 Eutropius became consul in the East with Valentinian II his co-consul in the West.
End of Eutropius:
A letter from Symmachus to Eutropius in 390 is the last living reference to him. Symmachus had edited Livy and so shared an interest in early Roman history.
Eutropius criticized Julian for his attacks on Christianity, but Eutropius was probably a pagan.
The Breviarium of Eutropius:
Eutropius' history or Breviarium covers Roman history from Romulus through the Roman Emperor Jovian, in ten books. Book I goes to the sack of Rome by the Gauls in 390; Book II ends with the end of the First Punic War; Book III ends with the end of the Second Punic War; Book IV ends with the Jugurthine War; Book V treats the period dominated by Marius and Sulla; the sixt book deals with Pompey; the seventh book ends with Domitian's assassination; the eighth book enhds with the death of Alexander Severus; the ninth book ends with the retirement of Diocletian; the tenth book ends with the death of Jovian.
The focus of the Breviarium is military, resulting in the judgment of emperors based on their military successes.
Sources: David Rohrbacher: The Historians of Late Antiquity
"Eutropius V. C. 'Magister Memoriae?'" R. W. Burgess, Classical Philology, Vol. 96, No. 1. (Jan., 2001), pp. 76-81.