The book opens in the year sixty-nine, following the death of Nero, chronicling the rapid rise and fall of Galba, Otho, and Vitellius. Tacitus sets out to explain the state of the Roman world, detailing the temper of the armies and the condition of the provinces. The narrative vividly depicts the deadly struggle for the throne that proved the Principate was based on armed force rather than constitutional fictions. The struggle culminates in the battles of Bedriacum and the tragic sack of Cremona, which sealed Otho's fate.
Beyond the civil wars in Italy, the second major movement details the dangerous rebellion of the Batavians and Germanic tribes on the Rhine frontier. The author focuses primarily on human character and the moral causes of Roman decadence, painting vivid psychological portraits of generals and emperors alike. Throughout the text, Tacitus illustrates how civil war dissolves law, relaxes discipline, and unleashes the worst passions of mankind. The narrative closes with the consolidation of power under the Flavian dynasty, leaving the reader with a bleak yet deeply instructive meditation on the fragility of political order and the heavy cost of ambition.