Despite all the excitement, one crucial element of Thucydides’s History of the Peloponnesian War seems so far to have escaped notice: Thucydides is an unapologetic elitist. He characterizes the establishment as moderate and sensible—all of the disasters that befall both Sparta and Athens in the History are brought about by populists. It is a delicious irony that Donald Trump’s camp, which rode to power on a wave of voter dissatisfaction with elites and angrily denounces experience as corrupting, is so beholden to a historian who demonstrates time and again that vibrant societies are brought to ruin by angry or enervated publics who ignore the moderating counsel of seasoned, educated elites.

Thucydides is often associated with hard-edged realism, as in the quote “the strong do what they will, the weak suffer what they must.” So it’s easy to see why politicians striking tough-guy poses profess their appreciation. But it’s important to remember that those views are one thread in a tapestry—Thucydides recounts the views of the war's combatants, but he doesn’t endorse them. In fact, the states that profess those hard-edged sentiments are plunged into ruin by them.

When and how they take the plunge has, at the crucial moments of decision, everything to do with rambunctious crowds or ambitious usurpers of their betters egging on policies that result in the destruction of their state’s power. The three major decision points of Thucydides’s History are Sparta’s decision to go to war with Athens; Athens’s destruction of Melos, a small state seeking to maintain neutrality; and Athens’s invasion of Sicily, which was allied to Sparta.

In the first instance, some of Sparta’s allies, a constellation of city-states called the Peloponnesian League, appeal to Sparta for protection from the gathering threat posed by a rising Athens. It’s important not to let modern conceptions of Athens as the birthplace of democracy sway our understanding too much: Athens was a predatory power, often in thrall to demagogues. Sparta, on the other hand, was a society ruled by law. Even the King and Ephor (an elected spiritual leader) were less powerful than the constitution, which is why the monument to the heroism of King Leonidas and his Spartans at the devastating Persian War battle of Thermopylae reads “go tell the Spartans, stranger passing by, that here obedient to their laws we lie.” Spartans were obedient to their laws, not their leader. Sparta was admired as a political culture and as an unobtrusive hegemon. Thucydides describes Athens as “tyrannical,” an incendiary term in the ancient world.

Athens revels in the threat it poses to Sparta’s allies. The Athenians brazenly show up at a meeting of the Peloponnesian League to rebut one small city-state’s plea for protection, saying “it has always been the law that the weaker should be subject to the stronger.” Athens rejects any sense of justice in the actions of states, basically saying it’s a cudgel that weak states use to restrain the strong. Sparta’s King, Archidamus, counsels restraint and urges carefully assessing the risks of war, but he loses the argument to Sthenelaidas, an elected Ephor who appeals to people’s fear of Athens and goads them into defending Sparta’s honor. If the entitled political class, rather than the populist, had been listened to, Sparta would not have gone to war with Athens.