Polybius

Polybius was a Greek historian of the second century BCE whose Histories traced Rome’s expansion and the Mediterranean world, including the Punic Wars.

Punic Wars: A series of three wars fought between Rome and Carthage from 264 to 146 BCE. Polybius’s surviving narrative is a central source for Rome’s wars against Carthage.
Mixed constitution: A political system combining elements of monarchy, aristocracy, and democracy. Polybius used this model to explain how Roman institutions balanced power.
Battle of Pydna: A 168 BCE Roman victory over the Macedonian king Perseus that ended the Third Macedonian War. The defeat led to Polybius’s deportation to Italy with other Achaean hostages.
Histories (Polybius): A forty-book Greek history by Polybius, covering events from 264 to 146 BCE. This is his principal work and the source of his account of Rome’s expansion.
Cicero: A Roman orator, statesman, and writer of the first century BCE. Cicero praised Polybius as an authoritative historian.
Roman Republic: The ancient Roman state governed through elected magistrates, the Senate, and popular assemblies. Polybius examined its institutions to explain Rome’s expansion.
Anacyclosis: Polybius’s theory that constitutions pass through a recurring cycle of political forms and their corruptions. His constitutional cycle frames the rise and decay of political systems.
Achaean hostages: A group of prominent Achaeans sent to Italy after Rome’s victory over Macedonia in 168 BCE. Polybius’s seventeen-year stay among them brought him into Roman political circles.
Battle of Cannae: A 216 BCE Carthaginian victory over Rome during the Second Punic War. Polybius gives a detailed account of Rome’s defeat and Hannibal’s tactics.
Livy: A Roman historian whose History of Rome recounted the city’s origins and expansion. Livy’s narrative overlaps with events preserved more fully by Polybius.

Linked from 50 pages