THE MASK OF COMMAND By John Keegan Elisabeth Sifton/Viking. 368 pp. $18.95

COMMAND," a favorite buzz word among today's military professionals and their critics, has at least three separate, though related meanings. It can be understood as a synonym for the act of military leadership, the manner or means whereby some men persuade, coerce or inspire others to follow their orders even at the risk of their lives. In another sense it means something very close to what is usually understood by the terms "strategy," "tactics" and "operational art"; that is, the methods and concepts which successful generals and admirals have employed to win battles and wars. Finally, command can be taken to mean the process through which military men organize, direct and communicate with their forces and keep themselves continually informed about their operations and those of the enemy. This process is often referred to by military professionals as "C I" (Command, Control, Communications and Intelligence). "C I" gives this whole complex system (which is often the first thing to break down in battle) a comforting scientific flavor.

John Keegan, the author of this latest book on command, is one of the most widely read and influential historians of modern war. His best known book, The Face of Battle, is especially well regarded for the new methods and perspectives which it brought to the study of military history. It is therefore more than a little surprising that in The Mask of Command he takes the most traditional of the three approaches to the study of command, viewing it as "the technique and ethos of leadership."

The bulk of the book comprises four long essays devoted to Alexander the Great, the Duke of Wellington, Ulysses S. Grant and Adolf Hilter -- the last, as an example of the pathology of command. None of these four figures has been exactly neglected by historians and Keegan appears to have attempted no new research beyond reading the standard biographies of his subjects and consulting the published editions of their writings. Nevertheless, as we have come to expect of Keegan, he has perceptive, illuminating and provocative observations to make about all four of his main characters. His portrait of Wellington, in particular, serves to bring to life this seemingly rather wooden giant of British history and resolves some of the apparent contradictions in his behavior. I also think his appreciation of Grant as a commander is essentially correct, although I am afraid his neglect of such recent works bearing on the subject as Michael C.C. Adams' Our Masters the Rebels, Richard Beringer and others' Why the South Lost, Gerald F. Linderman's Embattled Courage and Grady McWhiney and Archer Jones' Attack and Die is sure to leave him vulnerable to much sniping by the battalions of Civil War aficionados.

With his usual iconoclasm, Keegan begins his study by declaring that "I am a historian and not a social scientist and am therefore free to believe that the generalship of one age and place may not at all resemble that of another! . . . the warfare of one society may differ so sharply from that of another that commonality of trait and behavior in those who direct it is overlaid altogether in importance by differences in the purposes they serve and the functions they perform." This assertion notwithstanding, Keegan then proceeds to document rather persuasively the ways in which "commonality of trait and behavior" may be found in successful generals of widely varying circumstances and societies.

By the beginning of chapter two he is himself declaring that there has been "scarcely any change at all in the technique and ethos of leadership and command," in the 21 centuries from Alexander to Wellington! By the concluding chapter, Keegan is actually engaged in offering some broad general reflections on "the nature of military power, the means by which it is exercised and the process by which its effects are invested with political value." He appears in fact, to come perilously close to the attempt "to make universal and general what is stubbornly local and particular" which he warns us against in chapter one.

THE MASK of Command will almost certainly be compared with Martin Van Crevald's Command in War, a pioneering book which appeared in 1985 and has already become a kind of standard work. Despite the similarity in titles the Van Crevald and Keegan books have relatively little in common. Van Crevald was interested in "command systems," that is, the way in which commanders have attempted, through centralization or decentralization, to control large armies and make correct decisions in the face of incomplete and misleading information. Van Crevald is interested primarily in systems and organizations, Keegan in personalities and social relationships. Those looking for "C I" will find little of it in The Mask of Command, but those who are interested in a wise and insightful exploration of the tradition of heroic leadership in war, its cultural implications and its modern fate will profit from reading this book.

Ronald H. Spector, director of the Naval Historical Center, is the author of "Eagle Against the Sun: The American War With Japan" and, more recently, "U.S. Marines in Grenada."