Photo by JADE GAO/POOL/AFP via Getty Images History and geopolitics begin with the tectonic forces of geography, economics, military power, and so forth, that Paul Kennedy’s The Rise and Fall of the Great Powers (1987) conveys in a sweeping, brilliant manner. His reflection, 35 years after the book’s publication, is in its own way equally magisterial. However, as Kennedy himself suggests, global history isn’t only about grand deterministic forces, but about the scarcely predictable contingencies that arise from the psychologies and decisions of leaders themselves, who are often in the throes of passion when they make such decisions. This is...