The Reign of George VI, 1900–1925, published anonymously in London in 1763, makes for intriguing reading today. Twentieth-century France still groans under the despotism of the Bourbons. America is still a British colony. “Germany” still means the sprawling commonwealth of the Holy Roman Empire. As the reign of George VI opens, the British go to war with France and Russia and defeat them both. But after a Franco-Russian invasion of Germany, the war reignites in 1917. The British invade and subdue France, deposing the Bourbons. After conquering Mexico and the Philippine Islands, the Duke of Devonshire enters Spain, and a general peace treaty is signed in Paris on November 1, 1920.

The impact of revolution on the international system lies far beyond this author’s mental horizons, and he has no inkling of how technological change will transform modern warfare. In his twentieth century, armies led by dukes and soldier-kings still march around the Continent reenacting the campaigns of Frederick the Great. The Britannia, flagship of the Royal Navy, is feared around the world for the devastating broadsides of its “120 brass guns.” The term “steampunk” comes to mind, except there is no steam. But there are passages that do resonate unsettlingly with the present: English politics is mired in factionalism, Germany’s political leadership is perilously weak, and there are concerns about the “immense sums” Russian Tsar Peter IV has invested in British client networks, with a view to disrupting the democratic process.

Predicting future wars—both who will fight them and how they will be fought—has always been a hit-and-miss affair. In The Coming War with Japan (1991), George Friedman and Meredith Lebard solemnly predicted that the end of the cold war and the collapse of the Soviet Union would usher in an era of heightened geopolitical tension between Japan and the US. In order to secure untrammeled access to vital raw materials, they predicted, Japan would tighten its economic grip on southwest Asia and the Indian Ocean, launch an enormous rearmament program, and begin challenging US hegemony in the Pacific. Countermeasures by Washington would place the two powers on a collision course, and it would merely be a matter of time before a “hot war” broke out.

The rogue variable in the analysis was China. Friedman and Lebard assumed that China would fragment and implode just as the Soviet Union had, leaving Japan and America as rivals in a struggle to secure control over it. It all happened differently: China embarked upon a phase of phenomenal growth and internal consolidation, while Japan entered a long period…