THE RISE AND FALL OF THE GREAT POWERS Economic Change and Military Conflict From 1500-2000 By Paul Kennedy Random House. 676 pp. $24.95

PAUL KENNEDY advertises his intent to span the centuries from 1500 to the Strategic Defense Initiative, striding across cultures as varied as Ming China and the modern Soviet Union, with the Hapsburgs and other great powers in between. Actually he offers a fast gallop till 1815 in the first 140 pages, thereafter slowing down to consider the post-Napoleonic scene, going slower still after 1943, with half his pages devoted to the years since then. Still, why do it, if the result must be an exercise in superficiality? The answer is that large questions cannot be studied in a small compass, as per "Dutch Pin-Making, 1610-1611" and others such. But the historian who ventures across cultures and the centuries must have a good reason for doing so. Braudel, for example, wrote of the entire Mediterranean region because his goal was precisely to uncover the entire moving array of Mediterranean interactions, whether in the flow of credit or the interplay of mentalities.

Kennedy, who is J. Richardson Dilworth Professor of History at Yale, is not after interactions but comparisons, to answer the classic question: Why do the mighty fall? His answer, with many qualifications, is that they run out of cash, or its equivalent in men and horses, guns and ammunition, ships and ballistic missiles. As economies prosper and decline, the superstructure of state power built on them must also wax and wane. Kennedy is very careful not to argue that the costs of power are the cause of economic decline, and also avoids any crude mechanical correlation, fully acknowledging the importance of the skill with which statesmen and soldiers use whatever resources they have.

The result is a theory much superior to the ancient belief that powers rise and fall in a biological cycle from youth to decrepitude, but one also entirely unoriginal. Ever since the First World War with its decisive artillery barrages that were virtual extensions of shell-filling factory production lines, the nexus between economic capacity and military power has been universally understood. To reiterate that truth scarcely justifies either the superficiality imposed by too many years and too many countries, or 540 pages of text.

It turns out, however, that Kennedy's purpose is not historical at all, for he goes beyond explanations of the past to predict, and even admonish:

"The task facing American statesmen over the next decades, therefore, is to recognize that broad trends are under way, and that there is a need to 'manage' affairs so that the relative erosion of the United States's position takes place slowly and smoothly."

With that, everything falls into place. It is a sermon that we are reading, and the display of trans-cultural history serves the same purpose as the preacher's recourse to exotic references and learned asides: to gain authority for his injunctions. That the United States is in decline is too obvious for serious dispute, but it is not at all clear that its statesmen should accommodate the trend. The alternative, surely, is to reverse it, by drastically reforming society if needs be, or at least its educational and economic structures. Who knows? We could educate our children once again, restore quality in goods and services, and even redirect resources from frenetic consumption to productive investment.

Or has Professor Kennedy discovered historical laws which inflexibly govern our destiny? In that case, all efforts to avert further decline must indeed be futile, but then it is not history that we are dealing with but prophecy, and for that there is no need to first recount how the Hapbsburgs fared, or how two world wars were fought -- especially if these force an honest diplomatic historican like Professor Kennedy to delve into the details of military matters with which he struggles valiantly, not always with success.

To cite a small but revealing example, he hazards the statement that a French tank of 1940, the S-35 (mislabeled SOMUA-35 in the text, S.O.M.U.A. being the acronym of the manufacturer, not a model-name) was "of very good quality." Actually the S-35 shared the absolutely fatal defect of all French tanks of the time, namely that one man had both to command the vehicle and fire the gun, making the latter almost useless. True, reappraisals of 1940 overthrow the legend of German superiority in sheer weight of armor, and Professor Kennedy no doubt came across a mention of the S-35 in one of the texts he cites, written by one obviously innocent of any knowledge of tanks. In fact, Kennedy repeatedly relies on dubious sources, as in this case -- a prime exhibit of educational decline, a dissertation on French and German as well as British military doctrine accepted by a leading university, even though its author candidly admits his ignorance of French and German.

Such are the perils of writing history so broadly that secondary sources must be accepted at face value without even a glimpse at the documents, when indeed the result ceases to be history and declines into romance. Braudel wove his texts directly from the documents and limited his time horizon to the 16th century, yet historians warn us of his many errors large and small. We can still enjoy his parade of piquant details and choice anecdotes, but students of history must use his work with care whenever it drifts from what Braudel really knew, mainly Spanish economic history. Likewise, though Kennedy writes of many things it is diplomatic history till 1914 that he really knows, and for all things beyond that he is an uncertain guide. As for his prophecy, it seems plausible enough and it might do a lot of good if it inspires action.

But as he himself points out, no greater power stands ready to displace the United States, certainly not Japan whose leaders, quite rightly, refuse the honor. Besides, it is precisely a historian who should recall that great powers have their ups and downs before their final decline. After the loss of the American colonies, it was widely believed that British power was in decline, precisely on the eve of the Victorian ascendancy. And the reader of Tacitus would scarcely expect the survival of the Roman Empire for three centuries thereafter, any more than the Hapsburgs would have been credited with another hundred years after Austerlitz. In the language that we have now all learned, one simply cannot tell whether the last two decades are only a "correction" or the beginning of the end. Surely it depends on what we do.

Edward N. Luttwak, holder of the Arleigh A. Burke Chair in Strategy at the Center for Strategic and International Studies, is the author, most recently, of "Strategy: The Logic of War and Peace."