The Histories examines the early imperial period of Roman history. To fully understand Tacitus’s narrative, it is useful to know the events that preceded and succeeded the Year of the Four Emperors.

Rome was historically governed as a republic in which most policy decisions were made by a senate composed of the aristocracy. However, the republic underwent a crisis following the Roman conquest across the Mediterranean. A number of factors influenced the crisis, but the upshot was that generals began commanding armies personally loyal to them instead of the state. A protracted series of civil wars followed that lasted from the second century BCE until the victory of Octavian in 31 BCE. Octavian assumed the title of Augustus and consolidated power in his hands. His reign marks the beginning of the Principate (the rule of one emperor). His dynasty, the Julio-Claudians, ruled for nearly a century, which Tacitus describes much of in his Annals. This dynasty was overthrown in the reign of Nero, whose unpopularity and offensiveness led to a successful revolt against his rule in 68 CE. The success of this revolt is notable, as just over 20 years before, a provincial governor rebelled against the emperor Claudius and was promptly deposed by troops who were loyal to the Julio-Claudian dynasty.