Josephus, who introduced himself in Greek as "Iosepos (???????), son of Matthias, an ethnic Jew, a priest from Jerusalem", fought the Romans in the First Jewish-Roman War of 66–73 as a Jewish military leader in Galilee. Prior to this, however, he was sent as a young man in his early twenties for negotiations with Emperor Nero for the release of several Jewish priests. He later returned to Jerusalem and was drafted as a commander of the Galilean forces. After the Jewish garrison of Yodfat fell under siege, the Romans invaded, killing thousands; the survivors committed suicide.

According to Josephus, however, in circumstances that are somewhat unclear, Josephus found himself trapped in a cave with forty of his companions. The Romans asked him to surrender once they discovered where he was, but his companions refused to allow this. He therefore suggested a method of collective suicide: they drew lots and killed each other, one by one, counting to every third person. The sole survivor of this process was Josephus (this method as a mathematical problem is referred to as the Josephus problem, or Roman Roulette). Josephus and one of his soldiers then surrendered to the Roman forces invading Galilee in July 67 and became prisoners. The Roman forces were led by Flavius Vespasian and his son Titus, both subsequently Roman emperors. In 69, Josephus was released, and according to Josephus's own account, he appears to have played a role as a negotiator with the defenders during the Siege of Jerusalem in 70.

In 71, he arrived in Rome in the entourage of Titus, becoming a Roman citizen and client of the ruling Flavian dynasty (hence he is often referred to as Flavius Josephus — see below). In addition to Roman citizenship he was granted accommodation in conquered Judaea, and a decent, if not extravagant, pension. It was while in Rome, and under Flavian patronage, that Josephus wrote all of his known works. Although he only ever calls himself "Josephus", he appears to have taken the Roman praenomen Titus and nomen Flavius from his patrons. This was standard practice for "new" Roman citizens.

Josephus's first wife perished, together with his parents, in Jerusalem during the siege, and Vespasian arranged for him to marry a Jewish woman who had been captured. This woman left Josephus, and around 70, he married a Jewish woman from Alexandria by whom he had three male children. Only one, Flavius Hyrcanus, survived childhood. Josephus later divorced his third wife and around 75, married his fourth wife, a Jewish woman from Crete, member of a distinguished family. This last marriage produced two sons, Flavius Justus and Flavius Simonides Agrippa.

Josephus's life is beset with ambiguity. For his critics, he never satisfactorily explained his actions during the Jewish war ... why he failed to commit suicide in Galilee in 67 with some of his compatriots, and why, after his capture, he accepted patronage from the Romans.

Historian E. Mary Smallwood wrote:

(Josephus) was conceited, not only about his own learning but also about the opinions held of him as commander both by the Galileans and by the Romans; he was guilty of shocking duplicity at Jotapata, saving himself by sacrifice of his companions; he was too naive to see how he stood condemned out of his own mouth for his conduct, and yet no words were too harsh when he was blackening his opponents; and after landing, however involuntarily, in the Roman camp, he turned his captivity to his own advantage, and benefitted for the rest of his days from his change of side.

The works of Josephus provide crucial information about the First Jewish-Roman War and are also important literary source material for understanding the context of the Dead Sea Scrolls and late Temple Judaism. Josephan scholarship in the 19th and early 20th century became focused on Josephus' relationship to the sect of the Pharisees. He was consistently portrayed as a member of the sect, but nevertheless viewed as a villainous traitor to his own nation — a view which became known as the classical concept of Josephus. In the mid 20th century, this view was challenged by a new generation of scholars who formulated the modern concept of Josephus, still considering him a Pharisee but restoring his reputation in part as patriot and a historian of some standing. Scholarship post-1990 sought to move scholarly perceptions forward by demonstrating that Josephus was not a Pharisee but an orthodox Aristocrat-Priest who became part of the Temple Establishment as a matter of deference, and not willing association (cf. Steve Mason 1991).

Josephus includes information about individuals, groups, customs and geographical places. Some of these, such as the city of Seron, are not referenced in the surviving texts of any other ancient authority. His writings provide a significant, extra-Biblical account of the post-Exilic period of the Maccabees, the Hasmonean dynasty, and the rise of Herod the Great. He makes references to the Sadducees, Jewish High Priests of the time, Pharisees and Essenes, the Herodian Temple, Quirinius' census and the Zealots, and to such figures as Pontius Pilate, Herod the Great, Agrippa I and Agrippa II, John the Baptist, James the brother of Jesus, and a disputed reference to Jesus (for more see Josephus on Jesus). He is an important source for studies of immediate post-Temple Judaism and the context of early Christianity.

A careful reading of Josephus' writings allowed Ehud Netzer, an archaeologist from Hebrew University, to discover the location of Herod's Tomb, after a search of 35 years — above aqueducts and pools, at a flattened, desert site, halfway up the hill to the Herodium, 12 kilometers south of Jerusalem — exactly where it should have been, according to Josephus's writings.

For many years, the works of Josephus were printed only in an imperfect Latin translation from the original Greek. It was only in 1544 that a version of the Greek text was made available, edited by the Dutch humanist Arnoldus Arlenius. The first English translation, by Thomas Lodge, appeared in 1602, with subsequent editions appearing throughout the 17th century. However, the 1544 Greek edition formed the basis of the 1732 English translation by William Whiston which achieved enormous popularity in the English speaking world (and which is currently available online for free download by Project Gutenberg). Later editions of the Greek text include that of Benedikt Niese, who made a detailed examination of all the available manuscripts, mainly from France and Spain. This was the version used by H. St J. Thackeray for the Loeb Classical Library edition widely used today.

William Whiston, who created perhaps the most famous of the English translations of Josephus, claimed that certain works by Josephus had a similar style to the Epistles of St Paul (Saul).

• (c. 75) War of the Jews, or The Jewish War, or Jewish Wars, or History of the Jewish War (commonly abbreviated JW, BJ or War)
• (date unknown) Josephus's Discourse to the Greeks concerning Hades (spurious; adaptation of "Against Plato, on the Cause of the Universe" by Hippolytus of Rome)
• (c. 94) Antiquities of the Jews, or Jewish Antiquities, or Antiquities of the Jews/Jewish Archeology (frequently abbreviated AJ, AotJ or Ant. or Antiq.)
• (c. 97) Flavius Josephus Against Apion, or Against Apion, or Contra Apionem, or Against the Greeks, on the antiquity of the Jewish people (usually abbreviated CA)
• (c. 99) The Life of Flavius Josephus, or Autobiography of Flavius Josephus (abbreviated Life or Vita)

The Jewish War

His first work in Rome was an account of the Jewish War, addressed to certain "upper barbarians" — usually thought to be the Jewish community in Mesopotamia — in his "paternal tongue" (War I.3), arguably the Western Aramaic language. He then wrote a seven-volume account in Greek known to us as the Jewish War (Latin Bellum Judaicum). It starts with the period of the Maccabees and concludes with accounts of the fall of Jerusalem, the Roman victory celebrations in Rome, the mopping-up operations, Roman military operations elsewhere in the Empire and the uprising in Cyrene. Together with the account in his Life of some of the same events, it also provides the reader with an overview of Josephus' own part in the events since his return to Jerusalem from a brief visit to Rome in the early 60s (Life 13–17).

In the wake of the suppression of the Jewish revolt. Josephus would have witnessed the marches of Titus's triumphant legions leading their Jewish captives, and carrying treasures from the despoiled Temple in Jerusalem. He would have experienced the popular presentation of the Jews as a bellicose and xenophobic people.

It was against this background that Josephus wrote his War, and although this work has often been dismissed as pro-Roman propaganda (hardly a surprising view, given the source of his patronage), he claims to be writing to counter anti-Judean accounts. He disputes the claim that the Jews served a defeated God, and were naturally hostile to Roman civilization. Rather, he blames the Jewish War on what he calls "unrepresentative and over-zealous fanatics" among the Jews, who led the masses away from their traditional aristocratic leaders (like himself), with disastrous results. Josephus also blames some of the Roman governors of Judea, but these he represents as atypical: corrupt and incompetent administrators. Thus, according to Josephus, the traditional Jew was, should be, and can be, a loyal and peace-loving citizen. Jews can, and historically have, accepted Rome's hegemony precisely because their faith declares that God himself gives empires their power.

Jewish Antiquities

The next work by Josephus is his twenty-one volume Antiquities of the Jews, completed during the last year of the reign of the Emperor Flavius Domitian (between 1.9.93 and 14.3.94, cf. AJ X.267). He claims that interested persons have pressed him to give a fuller account of the Jewish culture and constitution. Here, in expounding Jewish history, law and custom, he is entering into many philosophical debates current in Rome at that time. Again he offers an apologia for the antiquity and universal significance of the Jewish people.

He outlines Jewish history beginning with the creation as passed down through Jewish historical tradition. Abraham taught science to the Egyptians, who in turn taught the Greeks. Moses set up a senatorial priestly aristocracy, which, like that of Rome, resisted monarchy. The great figures of the Bible are presented as ideal philosopher-leaders. There is again an autobiographical Appendix defending Josephus's own conduct at the end of the war when he cooperated with the Roman forces.

Against Apion

Josephus's Against Apion is a two-volume defence of Judaism as classical religion and philosophy, stressing its antiquity, as opposed to what Josephus claimed was the relatively more recent tradition of the Greeks. Some anti-Judean allegations ascribed by Josephus to the Greek writer Apion, and myths accredited to Manetho are also addressed.