The Jewish War (Greek: Φλαυίου Ἰωσήπου ἱστορία Ἰουδαϊκοῦ πολέμου πρὸς Ῥωμαίους βιβλία, Phlauiou Iōsēpou historia Ioudaikou polemou pros Rōmaious biblia), by Josephus is an account of the First Jewish-Roman War of 66-73 AD. Josephus had been the Jewish commander in Galilee before surrendering to Vespasian and defecting to the Roman side.
Free Online Texts
Gutenberg: The Wars of the Jews; Or, The History of the Destruction of Jerusalem by Josephus. Multiple formats.
Internet Archive: The Complete Works of Flavius Josephus, translated by William Whiston (1737). Multiple formats.
PACE: The Jewish War. Greek and English translation by William Whiston. HTML format.
Sacred Texts: The Works of Flavius Josephus, translated by William Whiston. HTML format.
Wikisource: The War of the Jews
Internet Archive: Josephus, by Norman Bentwich (Jewish Publication Society of America, 1914).
Librivox: The Wars of the Jews - public domain audiobook.
The Great Conversation: Further reading at Tom's Learning Notes
Tacitus: The Histories - Book V deals with the Jews and the Roman military campaign against them.
Ancient Greek resources: Learn to read Greek classics in the original.