As a dramatic study of men under pressure, singly and in groups, "Tour of Duty" is outstanding television. But things are not that simple. The men in groups are American soldiers serving in the Vietnam war, and because this is still such a touchy subject, the series, in trying to be all things to all factions, threatens to choke on caution.

Clearly one of the gutsier ventures of the new season, especially so for timid CBS, "Tour of Duty" premieres at 8 tonight on Channel 9. That puts it opposite "The Cosby Show," the cheerful juggernaut with a penchant for obliterating opposing forces. However, CBS found that "Cosby's" weakest demographics are among men; hence the scheduling of this male-oriented drama.

Shot in Hawaii on 16-mm film (so as to look something like news coverage of the war), "Tour of Duty" is distinguished by Class A performances and a tight, smart script. Success in television often boils down to the popularity of a character, and "Tour of Duty" is in good shape there thanks to Terence Knox, who comes off as tough-talking but fair-minded in the role of Sgt. Zeke Anderson, leader of Bravo Company.

Knox takes charge of the men and of the show and seems certain to come out of this alive, perhaps with a medal on his chest.

It would be the height of naivete' to deride "Tour of Duty" for failing to depict war in all its bloody and profane horror. In no way can a TV show emulate the realism, if that's what it was, of films like "Platoon," "Full Metal Jacket" and "Hamburger Hill." But within the understandable constraints of prime-time network television, "Tour of Duty" achieves an admirable level of gritty verisimilitude.

One line of dialogue, relating to racial tensions among the troops, is nothing if not mordant and raw. Walking into a tent filled with hostile faces, newly transferred Pvt. Ruiz (Ramon Franco) scowls, "What's the matter -- you niggers never seen a spic before?" Another reality of the war gets a passing reference when Sgt. Anderson is scouting for recruits and boasts, "I got boo-coo Vietnam dope." He's kidding.

The program is to some degree trapped between rocks. If it ignores the still-volatile issues of the war, the factors that made it so divisive on the home front, those passionate about them will consider the show a cop-out. But if it gets too deeply into those issues, "Tour of Duty" will merely do its part to prolong a very old debate and likely wade in over its head.

Writer-director (and co-executive-producer) Bill L. Norton's solution tonight is to achieve a rather homogenized balance. A war protester is among the draftees on hand -- "it's an unjust war," he says -- and he vows pacifism. But when chips are down in the closing scenes, and his life is threatened, he takes appropriate action.

"War is wrong," he says. "Maybe," says Sgt. Anderson. "But that's not the point." This cues a soulful reprise of Bob Dylan's "All Along the Watchtower." Earlier, a straight-arrow ROTC type says, "I don't think patriotism is something to laugh about, sergeant," and Anderson, apparently all things to all enlisted men, says, "Oh son, when it gets you into the fine mess you're into now, it is something to laugh about."

The appearance of having made a "statement" is sustained, even if no sort of statement really has been made.

This leads one to the suspicion that the more apolitical "Tour of Duty" is, the more effective it will be as drama. At moments, politics aside, it's quite brave. It introduces an extremely sympathetic character tonight and, before the hour is up, kills him off, because in a war, Vietnam or any other, people get killed.

Steve Duncan and L. Travis Clark, two bright young writers -- and Vietnam vets -- originally developed the idea for the series, to be called " 'Nam." CBS brought in Norton and fellow executive producer Zev Braun to make the concept more commercially palatable. People will argue about whether the producers have gone too far in that direction or not far enough. The fact remains: "Tour of Duty" is bold and affecting quality work.