In his 5th-century B.C. History of the Peloponnesian War, ancient Athenian historian and military general Thucydides posits, “it was the rise of Athens and the fear that this instilled in Sparta that made war inevitable.” It’s a musing that prompted American political scientist Graham T. Allison in 2012 to venture a theory known as the “Thucydides Trap,” noting that of 16 historical occasions when a presumptive power challenged an established one, no less than 12 resulted in war. Today, the “Thucydides Trap” is most often used to describe fractious U.S.-China relations and where they may lead—though it is a matter of hot debate.