THIS MASSIVE VOLUME is nothing less than the definitive institutional history of the United States Marines. It is the matured result of prodigious research and organization, relentlessly sober and fair-minded analyses and judgments, and the constant effacement of the powerful emotional charge the author -- a Marine reserve officer as well as a distinguished military historian -- brings to his work.

Curiously, the effect is partly polemical. Semper Fidelis is the history of a fighting corps which has expended far more lives and energies in justifying its combat record than in defending all the beachheads and quarterdecks and fire bases to which it has committed itself. And like all successful polemical works, the book creates and sustains its effects through careful accretions of data rather than by "arguing" its points. Dr. Millett in other words, is self-consciously obedient to the old novelist's cliche: "show, don't tell." He is not always successful, but then, neither has the simple enumeration of battlefield success and tactical innovations by Marine apologists been enough to persuade the Navy, the Congress, and the Defense Department to give them what they have needed to carry out their missions.

The Marines' fundamental institutional problem has always been two-fold. As a corps d'elite it is, simply, anomalous in liberal democracy, and therefore subject to remorseless scrutiny by government, press and public. From its beginnings it has been both hybrid and step-child: a seagoing infantry and, thus, the United States Navy's "own" military (as opposed to naval) force. As a consequence it has invariably been the first of the armed services to suffer in the aftermath of war: the obvious target of both Army officials -- who see their "own" combat missions replicated by forces not under their control -- and Navy personnel anxious to maintain their authority over an increasingly powerful but still "subordinate" force.

As a matter of fact, in recent history the Marines have been used only sporadically for what its contemporary planners have avowed are its missions. Perhaps never were those missions and capabilities more thoroughly ignored than in Vietnam, where the Marines were committed, as a self-contained force with their own air support, artillery, and logistical resources, to the conduct of an interminable ground combat on a huge scale.

For the Corps, the result has been paradoxical. For the United States, the Marines have been an enormously resourceful, dependable military instrument. As Dr. Millett's book makes plain, the Marine Corps' espirit and discipline is based on its unremitting sense that it must prove itself: prove itself by volunteering for missions and operations for which it is not always, strictly speaking, designed, and for which, invariably, it has not been properly equipped. The stormed and secured beachheads and islands of the Pacific War in the 1940s and the successful Inchon landing of 1950 stand as glittering anomalies in Marine history. Marine activity in World War I and Vietnam, and their like, in which Marine units were committed to operations essentially suited to the Army, have constituted normalcy along with the traditional duties of providing garrisons, guarding embassies and providing security -- "interior guard" -- for naval bases and ships.

The Marines have always been slighted by civilian and military planners. As the author notes, during the 11 years of its commitment in Vietnam, the "Corps share of the defense budget climbed only 8 percent while its contributions to military manpower climbed to 29 percent of military manpower." Marines now constitute 15 percent of American divisions and 12 percent of its tactical air forces for only 3.6 percent of the national defense budget.

And so "the history of the United States Marine Corps is essentially a story of institutional survival and adaptation in both peace and war." The author defines four phases in this chronicle: the first, from the American Revolution to the start of the 20th century, in which Marines guarded ships and barracks; the second, from their provision of "colonial infantry" in the aftermath of the Philippine annexation to the end of Marine service in Shangai, in 1941; a third phase, which somewhat overlaps the second, in which the Corps began development of its amphibious capabilities and later powerfully vindicated this work in World War II; and finally a fourth, in which the Marines are recognized as a "force in readiness," with multiple missions, but essentially those demanding the ability to move immediately to combat at short notice. As such, at least one Marine division is not committed to the Rapid Deployment Force, while other smaller units, usually of battalion size remain on station in the Mediterranean and Indian Ocean.

Semper Fidelis is history and apologia. Its author's narrative skills -- his accounts of combat operations -- are workmanlike and cautious. The familiar icons of legend -- the Chesty Pullers and Smedley Butlers -- are given only the most cursory attention. It is a jarring but thoroughly excusable lapse in methodology and tone that the book ends with an avowal that the essence of the institution's greatness is best evoked not by a sunset parade or the familiar recruiters' appeals but by a lone private in a barracks shower, late at night "after the raucous confusion of cleaning gear," whistling in the shower: whistling the Marine Corps hymn.