Once upon a time, the principal business of America was business. In our own time, America's business is the projection of global power.

This fact, made abundantly clear by events since Sept. 11, manifests itself in a number of ways. Whereas traditionally the State Department was the lead agency responsible for managing U.S. relations with the rest of the world, real clout these days resides in the Pentagon. Whereas American policymakers once professed to see the use of force as a last resort, today the Bush administration has enshrined a doctrine of preventive war as the centerpiece of U.S. foreign policy. Whereas in earlier times, perceived threats to American security determined the size, configuration and stationing of U.S. forces, today far gauzier and grander purposes -- for Bill Clinton, "shaping" the international environment; for George W. Bush, putting an end to evil -- dictate what sort of military we have and what we expect our soldiers to do. Whereas Americans used to count on those soldiers to defend the homeland, we have now assigned that task to an entirely new cabinet agency, freeing the armed services to focus on their actual post-Cold War mission, which is to coerce, pacify and influence others, everywhere from Kirkuk to Kabul and beyond.

All of this, according to Chalmers Johnson in this useful if also overheated and historically muddled book, is evidence of a new American militarism, a lamentable byproduct of an equally lamentable effort to forge a global pax Americana.

Johnson describes The Sorrows of Empire as "a guide to the American empire as it begins openly to spread its imperial wings." To be more precise, it provides an introduction to the military precincts of that empire.

In surveying those precincts, Johnson highlights several themes. They include the domination of the global arms market by U.S. weapons manufacturers; the increasing reliance on surrogates and mercenaries to conceal the full range of U.S. military activities; the lucrative and privileged status enjoyed by a handful of private contractors in supporting Pentagon activities abroad and the incestuous relationship between those contractors and high-ranking U.S. officials; the quasi-proconsular prerogatives exercised by regional U.S. military commanders; and the frequent antagonism engendered by America's sprawling military presence on every continent except Antarctica.

Little of this will strike specialists as new. Indeed, in assembling this account, Johnson draws freely from other published works, not least among them his own Blowback: The Costs and Consequences of American Empire, to which the present volume is something of a sequel.

His one original and genuinely important insight is to suggest that the several hundred U.S. military and intelligence installations scattered around the world define the boundaries of the present-day American imperium. In Johnson's view, the Pentagon's far-flung "empire of bases" constitutes the latter-day equivalent of the colonies, dominions and protectorates that defined empire in days of old. To plot the U.S. military presence around the world, in other words, is to map the American empire.

It is also to plot the locations of tomorrow's trouble spots. Johnson argues that the Pentagon's penchant for planting bases in weak countries governed by unpopular and brittle authoritarian regimes -- U.S. military activities in Central Asia and the Persian Gulf provide recent examples -- only serves to breed greater anti-Americanism and to incite further violence against U.S. interests, leading in turn to more interventionism, which requires still more bases and promotes the ever greater deeper militarization of policy.

When it comes to identifying the origins of this self-perpetuating cycle, Johnson is less persuasive. Indeed, he seems himself to be of two minds. On the one hand, he clearly wants to fix the blame for militarism and empire on the jingoists surrounding President Bush, who view the United States as "a new Rome, the greatest colossus in history, no longer bound by international law, the concerns of allies, or any constraints on its use of military force."

On the other hand, he confronts a historical record that does not sustain such a summary judgment: The Bush administration did not invent many of the military practices that Johnson deplores. They originated in World War II or even in the aftermath of the Spanish-American War. In short, American militarism, if that's what it is, has deep roots, extending back several decades at the very least. Thus, history considerably complicates the question of assigning responsibility for what Johnson clearly views as a perversion of U.S. policy. Indeed, it suggests the possibility that a militarized policy may not be a perversion at all, but an authentic expression of American statecraft.

Such ambiguities in no way reduce Johnson's willingness to declaim the apocalyptic fate that awaits Americans as a consequence of their present-day military infatuations. Likening our situation to that of the Soviet Union in the 1980s, he identifies four "sorrows" that he says "are certain to be visited on the United States." They are first, "a state of perpetual war"; second, "a loss of democracy and constitutional rights as the presidency fully eclipses Congress"; third, the rise of "a system of propaganda, disinformation, and glorification of war, power, and the military legions"; and fourth, national bankruptcy as "we pour our economic resources into ever more grandiose military projects." We are, in short, on a one-way road to perdition.

The role of the prophet is an honorable one. When a nation falls into sinful ways, angry words and dire prognostications may be necessary to reawaken the people to the truth. In Chalmers Johnson the American empire has found its Jeremiah. He deserves to be heard; but the proper response to his gloomy message is not despair, but thought followed by action.

Reviewed by Andrew J. Bacevich

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