Why is Tacitus’s Histories incomplete?

The Historiae (or Histories) by the Roman historian Tacitus is considered incomplete because only the first four books and a portion of the fifth book survive today. These extant sections cover the events of the years 69–70 CE.1

While the original work is estimated to have contained 12 or 14 books—covering the period from the beginning of 69 CE through the death of the emperor Domitian in 96 CE—the remainder of the text has been lost to history. Consequently, the specific details of how Tacitus chronicled the later years of the Flavian dynasty and his final assessment of Domitian's reputation remain unknown, representing a significant gap in the historical record.1