Polybius, a Greek who lived among the Romans, wrote The Histories to explain how Rome came to dominate the Mediterranean. This is Book 3. Book 2 left Hannibal in command in Spain after his father Hamilcar, Saguntum already in danger, and Rome planting colonies in the Po valley of northern Italy.

Hannibal, the Carthaginian, had sworn as a boy to fight Rome. He crosses the Ebro in Spain, the Rhone in what is now France, and the Alps in snow. He wins at the Trebia, then at Lake Trasimene, where the consul Flaminius — one of two officials elected to run Rome for a year — dies in the mist. Fabius delays and is hated for it. At Cannae the army is wrapped; some fifty thousand die, consul Aemilius Paullus falls, and Varro, the other consul, escapes. Capua and southern Italy peel away. The Senate of the Republic — Rome run by a senate and elected officials, not a king — will not break. Polybius asks what kind of state can lose that many men and still raise another army. You are walking into the worst day that Republic had yet survived.