"For a long time, certain prominent people in American politics and culture have, whenever the need to demonstrate that they have read a book, or even two, has arisen, turned to a common set of texts.
Sun Tzu’s The Art of War and Niccolò Machiavelli’s The Prince are old standbys.
The writings and speeches of Cicero, Homer’s epics, the works of Plato—really most of the major works of classical civilization—have vanished from the slimming libraries of America’s powerful and have thus fallen out of fashion. They are being replaced by the Harry Potter series.
One classical text that still gets dusted off every now and then is Thucydides’ History of the Peloponnesian War, whose popularity endures particularly in the foreign policy and military communities and, as Politico Magazine’s Michael Crowley reported Wednesday morning, among Donald Trump’s advisers: Thucydides is especially beloved by the two most influential figures on Trump’s foreign policy team.
National security adviser H.R. McMaster has called Thucydides’s work an “essential” military text, taught it to students and quoted from it in speeches and op-eds.
Mattis is also fluent in Thucydides’s work: “If you say to him, ‘OK, how about the Melian Dialogue?’ he could tell you exactly what it is,” [D.C. foreign policy veteran Graham Allison] says—referring to one particularly famous passage.
When former Defense Secretary William Cohen introduced him at his confirmation hearing, Cohen said Mattis was likely the only person present “who can hear the words ‘Thucydides Trap’ and not have to go to Wikipedia to find out what it means.”
The “Thucydides Trap” essentially boils down to a single insight: that powerful states are wary of increasingly powerful states. This fear regularly leads to wars. Deep stuff."