Polybius of Megalopolis, a Greek statesman held in Rome as a hostage, wrote The Histories to show how Rome, in about fifty-three years, came to rule the Mediterranean world. This is Book 2. Book 1 covered the First Punic War: Rome learned to fight at sea, beat Carthage off Sicily after twenty-three years, then crushed a revolt of Carthage’s unpaid mercenaries in Africa.

Gauls cross the Alps again and in 225, at Telamon in Italy, two Roman armies catch them and destroy them. Rome plants colonies along the Po in the north. Across the Adriatic, Teuta, queen of the Illyrians, learns Rome now polices those waters. In Greece, Aratus of Sicyon builds the Achaean League, a union of cities Polybius loved; Cleomenes III tries to restore Sparta and is broken at Sellasia by Antigonus Doson of Macedon. In Spain the Barcids — Hamilcar, Hasdrubal, then Hannibal — raise a new Carthaginian power. Hannibal takes the command. Saguntum, a city Rome has promised to protect, already stands in his way. Northern colonies and Spanish levies are the two jaws about to close.