Early manuscripts attest to Ambrose as the author of the five-book Latin version of the 'History of the Jewish War against the Romans', which Flavius Josephus had given in Greek in seven books. This attribution of the work, which has mostly run under the pseudonym 'Hegesippus' since around 830, is confirmed in this study by recourse to prose rhythm, particle usage, idiomatic word combinations, as well as the use and further development of classical quotations (as measured by Aelius Donat and Arusianus Messius) against today's communis opinio, and the origin (in Pannonian Sirmium) is narrowed down to the years 367-372.

The second part sheds light on the historiographical technique and historical interpretation of the early Ambrose, his demythicisation of the priestly prophet, general and historian Josephus, whose fictional self-stylisation as the god-sent herald of Vespasian's future he systematically banishes from his account. Detailed analyses explain the new structure of the work, its literary form based on the "classical" historians Sallust, Livy, Tacitus and Suetonius with a distinctly Vergilian and Sallustian colouring and the specifically Ambrosian view of the Roman generals and emperors from Pompey and Julius Caesar to Titus and Domitian.

Above all, however, is the image of the Christian interpreter of biblical, above all Old Testament writings, who, even before his episcopal office, sharpened Josephus' criticism of his fellow tribesmen who had deviated from the tradition of the fathers into an anti-Jewish polemic and, following Origen and Eusebius, developed a concept of history in which the Jewish-Messianic expectation of salvation was overtaken by the appearance of Christ.