The Vietnam Guilt Trip is one that Americans may justifiably feel they have taken often enough.

In print, former Marine lieutenant Philip Caputo's journal of the war years had value for its personal, combat-zone perspective on disillusionment. But turning it into a TV movie was a mistake, to judge from the result: "A Rumor of War," the two-part, four-hour CBS film at 9 tonight and Thursday on Channel 9.

Both morose and glib, the film imposes narrative demands on Caputo's book that it cannot -- at least as John Sacret Young has adapted it -- support. "Rumor" turns a firsthand account into hearsay and a graphic chronicle inot a whining bill of particulars. Young and director Richard T. Heffron have complained of network meddling with the finished film, but this may be a case where commercial compromise would be preferable to didactic self-righteousness.

After an unaffecting prologue in which the hero, at 22, cuddles on a couch with his girlfriend in 1963 and hears that "he's dead, JFK is dead" from the TV set, the young innocent enlists in the Marines and is sent to boot camp, where the film is shocked to discover that men are actually trained to defeat an enemy in combat.

"Kill!" bellows a drill instructor. "The lesson for today is, Kill!" He indoctrinates Caputo in this barbaric theology: "Kill!" "Yes, sir!" "Kill!" "Yes, sir!" "Kill!" "Yes sir!" And so on. Presumably the Vietnam war would not have left such a scar of shame if the Marines had been trained to go in there and set up rap sessions and encounter groups with the VC.

That Vietnam was a dirty little war is not precisely a hot bulltine at this point, nor is there much irony in having one soldier repeatedly refer to it, sarcastically it appears, as a "splendid little war." Caputo's progress from eager young soldier to embittered cynic, if that is progress, proceeds ponderously and rarely with the urgency achieved by, for instance, last year's "All Quiet on the Western Front," which of course was about a dirty big war.

Caputo sees a comrade die from the intense hear, listens to a general demand that a pit he dug so he can play horseshoes and balks when told to drag in dead enemies for a body count ("Couldn't we just bury the poor bastards?"). Soon after he and his fellow Marines are offered extra beer for extra kills, he goes crazy; he authorizes a small raid on an innocent village and is later charged with, and cleared of, murder for the deaths of two villagers.

Brad Davis plays Caputo with the same blank, hangdog mope already overexposed to the breaking point in "Midnight Express." He is a monotonously uninteresting actor, unimposing to the point of invisibility and awfully short, it would seem, to be a Marine lieutenant in the first place. Keith Carradine as a buddy is similarily ineffectual. The best actors tend to play characters who quickly get killed, war being war; when it is said of the resourceful hulk Brian Dennehy, as Sgt. Coleman, that "you just plain liked him" and "he'd been there," you know there's a bullet with his name on it just a few script pages away.

When he's hit, Dennehy has one of the film's lamentably few moving scenes. "I'm history," he says to his men, urging them to take cover and forget him.

Because this is television, the marines can't use the words one expects marines would use in these circumstances. Apparently "butt" was given the okay by standards and pratices, however, so the term is constantly popping up -- "off your butts," "off their butts," even "blew his butt away." At one point someone is called a "dip head." But a breakthrough of sorts is accomplished in part II when Davis will be permitted to say on national network TV (to a Viet Cong), "Screw you and screw your Uncle Ho."

The film lacks the dimensions of tradegy or the authenticity of journalism. Although it is true that TV dramas have not so far dealt in substantial, revealing ways with the Vietnam war from the soldier's point of view, "Rumors" does not comprise an overdue examination. It veers more toward sermonette, although the voice-over narration aspires to a self-pitying and yet self-glorifying pulp-poetry:

"They look so young, so clean, just arriving," says Caputo as he is about to leave Da Nang, "but the silver coffins and I, we were leaving together." And: "I had learned all about death -- too early, too quickly." If you're going to drag up the subject of the Vietnam war for four hours on network television, it should provide more than an excuse for bad writing and bad acting and hearts sewn too proudly on sleeves.