FOR a superpower, dealing with the fast rise of a rich, brash competitor has always been an iffy thing.

Just ask the British, who a century ago were struggling to come to terms with the erosion of their status as the world’s No. 1 empire. It didn’t help that they were being upstaged by a former colony that had turned into an upstart sea-power with money, talent, and a knack for mangling a perfectly good language. Eventually they took the hit to the national ego from those Americans and discovered there were advantages to no longer playing the role of the indispensible power.

Or ask Thucydides, the Athenian historian whose tome on the Peloponnesian War has ruined many a college freshman’s weekend. The line they had to remember for the test was his conclusion: “What made war inevitable was the growth of Athenian power and the fear which this caused in Sparta.”...