The study of Thucydides and his famous History of the Peloponnesian War has never been so intense, so widespread or influential, as in our time. Thucydides claimed that his work is “a possession forever” meant to be useful to “such men as might wish to see clearly what has happened and what will happen again, in all human probability, in the same or a similar way.” More than twenty-four-hundred years later, political leaders and students of politics treat it in just that way.

In the ancient world, Thucydides’ focus on politics routed the broader but shallower purview of his predecessors. Herodotus, with his meandering style full of discursive side trips into the customs and habits of various peoples and his serious consideration of the causal role of the gods in human affairs, did not become the model for what was thought to be the best historical writing in antiquity. Polybius and the Romans Sallust, Livy, Tacitus, and Ammianus Marcellinus were the great classical historians, and they wrote chiefly about their own times, their own nations, and, especially, about war and politics.

During the Renaissance and the early modern period of European history, Polybius, whose history of Rome’s conquest of the Mediterranean world followed the Thucydidean model, and Tacitus, who focused on politics in Rome, were the favorites. In the seventeenth century, Thomas Hobbes published the first complete English translation of Thucydides’ History directly from the Greek original. “Thucydides,” he said, “is one, who, though he never