THREE DECADES ago, a German history professor listed 210 proposed explanations for the fall of the Roman Empire. The remarkable array included such fanciful causes as Bolshevism, public baths, hedonism, the pressure of terrorism and, most famously, lead poisoning. The last explanation has been discredited. It is highly unlikely that lead water pipes caused the ...

For years, many believed that a world of global economic networks and interdependence — countries intimately connected via supply chains and finances — made war obsolete. That is part of the reason Russia’s invasion of Ukraine was so shocking. But the international economy itself has turned into a battlefield. The conventional war in Ukraine has ...