IN WHICH WAR was the term "Gook" invented? When did American soldiers conduct their first body count and pioneer the use of the "water cure" to persuade Asian guerrillas to betray their comrades?

After which battle did a young rifleman write home to the folks in Kingston, New York, "I am in my glory when I can sight my gun on some dark skin and pull the trigger"?

Modern as it all sounds, the answer is not Vietnam, or even Korea or World War II. The American conquest of the Philippines barely rates a mention in school history books, usually as a cryptic footnote to the short war which President William McKinley and publisher William Randolph Hearst waged on Spain in 1898 for the independence of Cuba and the circulation of Hearst's newspapers. Yet 126,458 Americans fought in the Philippines between 1898 and 1902, of whom 4,234 died, while 16,000 Filipinos died in battle and another 200,000 in "reconcentration camp." There were in addition massacres of civilians in reprisal for guerrilla attacks and similar sideshows all too familiar in subsequent Asian wars.

The story of how, and why America liberated the Philippines from Spain and then took the islands back from their inhabitants two weeks later is a complicated one, already well told in one of the classics of American historiography, Leon Wolff's Little Brown Brother, published in 1960. But the writing of history is never finished, and David Haward Bain has managed another fine book on the subject, not disagreeing with Wolff's conclusions, but making them fresh and vivid for a generation which has seen yet another Asian war.

This is not, however, simply another tale of savagery in the rice paddies. Almost as if he could read tomorrow's newspapers, Bain has brought his account up to the minute, with perceptive entries, for instance, indexed under Aquino Benigno and Ver, General Fabian (the latter currently on trial for complicity in the former's assassination). This energetic young historian has thus pulled off that rarest of publishing coups, a scholarly historical work of bang-on topicality. He has, what's more, found a most original way of bringing his story to life.

From this distance, and even at the time, the American conquest of the Philippines has always been difficult to fathom. But, then and now, two figures jump forth from a cast of thousands: Emilio Aguinaldo, not quite 30, brave and passionately patriotic, the president of the republic of the Philippines proclaimed as the beaten Spaniards departed (and the first republic in Asia) and Colonel Frederick Funston, six years older, who drove the last nail into the republic's coffin by capturing Aguinaldo on March 23, 1901, after a long and daring hunt through the jungles and mountains of northern Luzon.

Aguinaldo, who looked remarkably like his current successor, Ferdinand Marcos, survived his capture and lived a long life, long enough to welcome the arrival of the Japanese in 1942 (understandably, perhaps; the new invaders also promised liberation), to march in the Manila independence parade of 1946, carrying the flag he first raised against Spain in 1896, and to see a new American war just getting under way in Asia in 1964, the year of his death. A largely forgotten figure now, even in the Philippines, Aguinaldo emerges from Bain's book an authentic hero and his republic a tragically missed chance for the United States to have been the protector of Asia's first genuine democracy.

His captor, the adventurous son of a Kansas politician known as "Foghorn Funston, the farmers' friend" was plainly just as archetypal a figure. "I am afraid that some people at home will lie awake nights worrying about the ethics of this war, thinking that our enemy is fighting for the right of self-government" he told a New York Times correspondent. "The word independent, which these people roll over their tongues so glibly, is to them a word, and not much more . . . . they are, as a rule, an illiterate, semisavage people, who are waging war, not against tyranny, but against Anglo-Saxon order and decency." Funston's feat, a mixture of reckless daring and ingenious double-cross, or what used to be known in Vietnam as a "John Wayne stunt," was the stuff of movies, and would have made a splendid vehicle for James Cagney (Funston was 5 feet 4 inches tall and touchy about it) if Hollywood had blossomed before American imperialism went out of fashion.

BUT, LIKE MANY a veteran from the East, Funston could not settle down to life back home, took to the bottle and died at 51 in 1917, when he was being seriously considered for command of the American Expeditionary Force that went to France that year. But for his heart attack, in fact, we would very likely now be debating the merits of the Funston rocket instead of the one named for his deputy, General John Pershing, who got the job instead.

Here, unmistakably, we have the Green Beret, or cowboy turned romantic military stuntman. In fact, Funston's boss, General Arthur MacArthur, father of the even more famous Douglas, was an old Indian fighter, and so were many of his buddies in the 20th Kansas infantry he led to the Philippines. The fact that the Far East is West of the Wild West has profoundly shaped America's wars there, a point made in the insightful and absurd movie The Deer Hunter.

It is hard to quarrel with Bain's conclusion that the years of American rule did little or nothing to solve the basic political problem of the Philippines. After three centuries of Spanish colonial government, the islands had none of the institutions of self-rule and no experience of it. All the new rulers achieved was a superficial Americanization of the illustrades, the Hispanicized native upper class, leaving the masses in pious poverty and the way open for a native-born dictatorship to follow the authoritarian rule of slippery Spaniards and decent Anglo-Saxons. People learn self-government by governing themselves and making their own mistakes, and America put off the Philippines' fateful day for 50 years, failing, in the end, even to supply the military protection that is the only justification for empire.

But Americans are still well thought of in the Philippines, as Bain and a group of friends, including his photographer-brother Christopher, discovered when they repeated Funston's epic trek through the Luzon jungle in 1982, talking to the same locals, fording the same streams, and being bitten by descendants of the same mosquitoes which bit the pint-sized adventurer and his party 80 years earlier. Melding past and present, and interweaving the historical background with present politics brings vividly home the long shadows still cast by America's first adventure in Asia. This is an important story, honestly researched and well told -- a second classic, in fact, on a fascinating subject.