FROM CHIVALRY TO TERRORISM: War and the Changing Nature of Masculinity, by Leo Braudy. Knopf, 613 pp.

Google permits the most unlikely people to display sudden bursts of erudition. Not long ago, I came across the blog kept by a generic urban hipster -- one containing the familiar catalog of new CDs purchased, smirking remarks on public affairs and essentially meaningless references to "irony." (Memo to the clueless: Irony does not mean repeating cliches in a sarcastic manner. It just doesn't.) Reading a few entries, I got the strong sense of someone whose powers of concentration were utterly focused on the Next Big Thing.

Then, erupting strangely into this mix of au courant gesturing and posturing, the blogger somehow contrived to deliver a (suspiciously detailed) lecture on an episode from ancient Greek military history. The recitation of battle manuevers looked odd mixed in there with the Britney Spears references. And then I realized what probably had happened: In an effort to add a hint of sophistication, the blogger cribbed from an online encyclopedia, thereby sounding encyclopedic. It was a reminder that all of culture now exists in byte-sized pieces -- pre-chewed by search engines, serving as instant nourishment for the hungry ego.

And so Leo Braudy's book on the cultural history of warfare lumbers onto the scene like a dinosaur, moving at its own unhurried pace -- a curious sight in an era of overburdened (and miniaturized) attention spans. The subject of warfare is timely. Braudy's method is not. He avoids the contemporary sense of the term "culture," which treats it as a menu of available kinds of information and entertainment. Braudy's writing seems to be informed, rather, by T.S. Eliot's notion of cultural tradition as something that develops slowly -- and that you don't just "acquire," like any given commodity, but must work to assimilate.

That sounds like a conservative outlook. But From Chivalry to Terrorism bears only a superficial resemblance to books such as Donald Kagan's recently reprinted On the Origins of War and the Preservation of Peace (1995) and Victor Davis Hanson's Carnage and Culture: Landmark Battles in the Rise of Western Power (2001). Both of those books embody a deep knowledge of military history, as reflected through a political sensibility that is definitely to the right. For them, war is a time of facing hard truths about human existence, and since that kind of truth doesn't change over time, neither, at the deepest levels, does war.

Braudy's emphasis, by contrast, is on the relationship between masculinity and the martial spirit -- and how both have changed in human history. This might seem counterintuitive to the feminist as well as to the conservative. After all, the perennial link between testosterone and combativity is the stuff of jokes. (See, for example, Dr. Strangelove, in which a crazed general launches the H-bomb at the Commies from fear they are corrupting his "precious bodily fluids.")

But warfare is not simply a fistfight on a much grander scale. Braudy's argument is (to put it a bit paradoxically) that men don't make wars, but vice versa. What men and women alike understand by "masculinity" at any given moment in history is profoundly shaped by the experience of combat. At the same time, the experience of warfare is always horrific; most men get through it only because of the powerful cultural sanctions against being unmanly. "Wars consume resources," writes Braudy, "but they also consume men, and they feed especially on the idea that men naturally go to war -- an idea that enshrines a masculine heroism that will inspire men to go to future wars."

The warrior ethos is a product of culture, then, not of biology. As the conditions of combat change, so, by a kind of relay system, does the whole society. In the ancient and medieval worlds the masculine value of honor had been modeled upon the individual bravery of warriors of noble social origins who fought on battlefields that brought enemies in fairly close proximity to one another. All of that began to change at an intense pace in the 16th and 17th centuries, when the new world view of nationalism combined forces with innovations in military technology.

Gunpowder meant the power to deal death at a distance. The military elite might still think of the infantry as "scum." Yet, the need for troop cohesion meant that even the lowlifes had to feel that they could gain honor from victory. Nationalist and democratic sentiment thus fueled one another in the heat of combat, then spilled over from the battlefield into postwar life.

The problem with reducing Braudy's book to the skeleton of its argument is that the history he describes is much less neat and orderly than I am making it sound. In the preface to Native Informant, a collection of his essays that appeared in 1991, Braudy noted that one problem with academic writing (its "great lie," as he put it) was that "it makes typographic linearity seem like a necessary causality of ideas." That is, the fact that sentences on the page move steadily foreward, line by line, can trick us into thinking that our understanding of the world develops in an equally straightforward fashion.

In From Chivalry to Terrorism, Braudy's narrative looks, at first, as if it is marching in an orderly line from ancient Greece through the "War on Terror." But in fact, the development is a lot more complex than that. Cultural history twists around like a pretzel. As new weapons of mass destruction emerge, the organization of combat changes. So does the structure of the army -- and with it the way authority and duty are understood by soldiers and civilians alike. When the male ideal of the warrior changes, so do the accepted ideas about women's roles. The most intimate sense of the individual's self is ultimately shaped by the terrors of the killing field.

Braudy draws upon roughly 3,000 years' worth of literary, artistic and cinematic references. They are not treated as documents recording the experience of warfare in any given period. Rather, each proves to be a site of combat itself -- a zone in which the essential values of a society are being forged in conflict. It is a demanding notion of what culture is, or could be. The product is a book that, in its display of a genuinely learned mind at work, reminds us that there is more to erudition than having instantaneous access to information.