In the early 1910s, British Foreign Secretary Edward Grey was surveying the world from his office in Whitehall. He saw many minor wars, but nothing that would pit the great powers at the time against one another. Even “in the early months of 1914 the international sky seemed clearer than it had been,” he later wrote in his memoirs. World War I, of course, broke out just months later, and went on to kill 40 million people. Almost nobody saw it coming, but many, including Lord Grey, concluded