• People have learned to live with the knowledge that they will die. But the evidence that entire nations, apparently invincible behemoths, may be similarly fated has proved the source of enormous curiosity and awe. The Old Testament exclamation "How are the mighty fallen!" was only one of the earliest recorded responses to the spinning wheel of fortune. Ever since, the rubble of old realms has teased and provoked imaginations. In the 18th century, a visit to Rome inspired Gibbon to write an enduring history of imperial decline. Romantic poets found the gloom and doom of antiquity irresistible. Envisioning an ancient toppled monument in a barren desert, Shelley conceived an epitaph that was both ironic and admonitory: "My name is Ozymandias, king of kings:/ Look on my works, ye Mighty, and despair!" In a softer temper, Poe allowed the face of a beautiful woman to transport him back in time "To the glory that was Greece,/ And the grandeur that was Rome."

    The spectacle of eclipsed civilizations leads not just to poetry and nostalgia but also to a practical consideration: Is it possible to beat the odds that the past has so clearly posted? One answer is suggested in a new volume that U.S. policymakers and pundits are lugging around in their briefcases, an immense academic history bristling with tables, maps and charts, plus 83 pages of closely printed footnotes and a bibliography that cites nearly 1,400 sources. The book is The Rise and Fall of the Great Powers, by Yale Professor of History Paul Kennedy. Its message, particularly for the U.S. at the present moment, is not encouraging.

    Kennedy's study is actually two books in one. The subtitle -- "Economic Change and Military Conflict from 1500 to 2000" -- accurately describes the , bulk of the contents: a sweeping survey of the shifting balance of power over five centuries. The book could easily serve as an introductory history text for very bright undergraduates. But Kennedy is not content to end his story in the present. His final chapter, "To the 21st Century," ventures to predict which nations will prosper and decline in the near future. Astrologers do this sort of thing all the time; when a respected historian tries his hand, people pay attention.

    Kennedy's view of the past, and of the years to come, is governed by a central and, on the surface, astonishingly simple thesis: "The historical record suggests that there is a very clear connection in the long run between an individual Great Power's economic rise and fall and its growth and decline as an important military power (or world empire)." If all he were saying is that richer nations tend to win wars, then there would be very little reason for anyone to read further. But Kennedy's argument is more supple than it at first appears. A nation's strength, both in its commerce and on the battlefield, must be measured against that of its rivals and enemies: "So far as the international system is concerned, wealth and power, or economic strength and military strength, are always relative . . . and since all societies are subject to the inexorable tendency to change, then the international balances can never be still."

    Hence, Kennedy detects a pattern repeated over and over: "Wealth is usually needed to underpin military power, and military power is usually needed to acquire and protect wealth." While worrying about their foes, states playing in the world arena must constantly maintain a delicate internal equilibrium. Armies are required for security, but they cost money. Military superiority by itself is often deceiving, since it may be weakening a state's ability to compete economically and fund future conflicts.

    Read this way, European history looks subtly different. Supposedly decisive battles such as the destruction of the Spanish armada in 1588 or Napoleon's defeat at Waterloo in 1815 seem instead to be foregone conclusions, the visible death throes of nations that had previously mismanaged or squandered their resources. Kennedy does not subscribe to the "Great Man" theory of history. He acknowledges that his account of the Napoleonic wars tends "to downplay the more personal aspects of this story, such as Napoleon's own increasing lethargy and self-delusion." But the author insists that inspiring < leaders or brilliant generals can at best cause momentary glitches in the relentless "dynamic of world power," which entails constant change both within and between nations. "Those are not developments," Kennedy warns, "which can be controlled by any one state, or individual."

    The Rise and Fall of the Great Powers is sure to generate considerable discussion and debate among professional historians. Amateur spectators will probably concentrate on what the coming decades are supposed to hold. Americans, specifically, have noticed over the past few years that wide swatches of the rest of the world are turning from obedient clients into uppity competitors. Trade imbalance, budget deficits, falling currency, skyrocketing military expenses now conspire to trouble the American dream. There is a nagging fear that things are coming unglued, and Kennedy does little to allay it.

    He argues that the combination of the U.S.'s declining rate of industrial growth and its extensive military commitments spells trouble: "Decision- makers in Washington must face the awkward and enduring fact that the sum total of the United States' global interests and obligations is nowadays far larger than the country's power to defend them all simultaneously." Even aside from this dilemma, American dominance is on the wane, not because the nation is growing poorer or weaker but because others are becoming richer and stronger. Kennedy expects both China and Japan to improve their shares of world power; if the European Community can submerge national disputes and agree on common goals, then it too will find its wealth and influence increasing. The Soviet Union possesses a vast military machine and a stagnant economy; uh-oh for the U.S.S.R.

    America's comparative decline in the international pecking order will not imply a lapse of national drive or purpose: "It simply has not been given to any one society to remain permanently ahead of all the others." Furthermore, enlightened leadership should be able to detect changing realities and thus prevent a slide from turning into a crash: "The only serious threat to the real interests of the United States can come from a failure to adjust sensibly to the newer world order." Not everyone will welcome or accept Kennedy's bittersweet verdict that the U.S. may become healthier in the long run by accepting its diminishing status gracefully. But until it is convincingly refuted by other theorists or the years ahead, The Rise and Fall of the Great Powers stands as a fascinating response to ancient questions about the life- span of nations.