When Barack Obama meets this week with Xi Jinping during the Chinese president’s first state visit to America, one item probably won’t be on their agenda: the possibility that the United States and China could find themselves at war in the next decade. In policy circles, this appears as unlikely as it would be unwise.
And yet 100 years on, World War I offers a sobering reminder of man’s capacity for folly. When we say that war is “inconceivable,” is this a statement about what is possible in the world—or only about what our limited minds can conceive? In 1914, few could imagine slaughter on a scale that demanded a new category: world war. When war ended four years later, Europe lay in ruins: the kaiser gone, the Austro-Hungarian Empire dissolved, the Russian tsar overthrown by the Bolsheviks, France bled for a generation, and England shorn of its youth and treasure. A millennium in which Europe had been the political center of the world came to a crashing halt.
The defining question about global order for this generation is whether China and the United States can escape Thucydides’s Trap. The Greek historian’s metaphor reminds us of the attendant dangers when a rising power rivals a ruling power—as Athens challenged Sparta in ancient Greece, or as Germany did Britain a century ago. Most such contests have ended badly, often for both nations, a team of mine at the Harvard Belfer Center for Science and International Affairs has concluded after analyzing the historical record. In 12 of 16 cases over the past 500 years, the result was war. When the parties avoided war, it required huge, painful adjustments in attitudes and actions on the part not just of the challenger but also the challenged.