In his new biography of Henry Kissinger, the historian Niall Ferguson recalls that halfway through what became an eight-year research project, he had an epiphany. Tracing the story of how a young man from Nazi Germany became America’s greatest living statesman, he discovered not only the essence of Kissinger’s statecraft, but the missing gene in modern American diplomacy: an understanding of history.

For Ferguson, it was a humbling revelation. As he confesses in the introduction to Kissinger: “In researching the life and times of Henry Kissinger, I have come to realize that my approach was unsubtle. In particular, I had missed the crucial importance in American foreign policy of the history deficit: The fact that key decision-makers know almost nothing not just of other countries’ pasts but also of their own. Worse, they often do not see what is wrong with their ignorance.”

Ferguson’s observation reminded me of an occasion three years ago when, after an absence of four decades, Kissinger returned to Harvard. Asked by a student what someone hoping for a career like his should study, Kissinger answered: “history and philosophy”—two subjects notable for their absence in most American schools of public policy.

How did Kissinger prepare for his first major job in the U.S. government as national security advisor to President Richard Nixon? In his words, “When I entered office, I brought with me a philosophy formed by two decades of the study of history.” Ferguson uncovered a fascinating fragment from one of Kissinger’s contemporaries when they were both first-year graduate students at Harvard. John Stoessinger recalled Kissinger arguing “forcefully for the abiding importance of history.” In these conversations, Stoessinger said, Kissinger would cite the assertion by the ancient Greek historian Thucydides that “The present, while never repeating the past exactly, must inevitably resemble it. Hence, so must the future.”

“More than ever,” Kissinger urged, “one should study history in order to see why nations and men succeeded and why they failed.” ...