“The relative strengths of the leading nations in world affairs never remain constant, principally because of the uneven rate of growth among different societies and of the technological and organisational breakthroughs which bring a greater advantage to one society than to another.” So wrote the British-born Yale historian Paul Kennedy in his book The Rise and Fall of the Great Powers published in 1988. It had an astonishing success, selling two million copies worldwide, principally because of the 20-page postscript added at his publisher’s prompting.

Entitled The United States: The Problem of Number One in Relative Decline, it compared the management problems facing the US to those of imperial Spain and Britain and asked whether it was adequately prepared for the imperial overstretch that faces great powers when uneven growth shifts their relative position.

It stimulated a fevered debate about how the US would balance its wealth, economic base and worldwide strategic commitments, as it faced competition from the Soviet Union, Japan, a reviving EEC and an emerging China. That it happened just before the Soviet bloc exploded and its regime collapsed and Japan peaked before a long relative decline took some credibility from Kennedy’s analysis. But this does not undermine its continuing salience for understanding great-power rivalry and positioning.........

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