As an issue and as a memory, Vietnam is still strewn with land mines. It was beginning to look as if the subject were beyond the reach of Hollywood and its fictions, but now a lowbudget and largely unheralded movie, "Go Tell the Spartans," has arrived at several area theaters and taken a few small but devastating steps toward the light at the beginning of the tunnel.

The film is surprisingly powerful and convincing, despite a script that may itself be too spartan and the mechanical hand of a computerized director, Ted Post ("Beneath the Planet of the Apes"). Much of the impact, for better or worse, derives from the commanding presence of Burt Lancaster. "Spartans" marks his 60th starring film role. Old blood and guts gets a chance to demonstrate here that he still has undeniable, if also mildly wacky, authority on the screen.

Naturally there are oversimplifications in the script by Wendell Mayes, from the novel "Incident at Muc Wa," by Daniel Ford. But Mayes has not stepped four-square into the booby traps already occupied by the filmmakers who did "Coming Home," in which the entire war was personified in the character of a self-loathing psychotic, or "The Boys in Company C," in which audiences were told that America lost the war but won the soccer game.

Mayes does set up a few embarrassing sitting ducks - a medic whose name happens to be Abraham Lincoln and who smokes marijuano from a rustic pipe, a gung-ho jingoistic lieutenant who says things like, "We won't lose, we're Amurricunns" and

talks of winning "the hearts and minds" of the Vietnamese people, and others.

But if a number of the men ring false, a greater number ring poignantly true. And, standing crotchety and tall in their midst, as the major who's seen it all and is referred to by his men as "World War II." Lancaster manages to be both imposingly larger than life and possessed of a trenchant kind of pathos.

It helps that the film limits itself to a narrow strip of geographical and narrative terrain and doesn't try to sum up the war or everything it may have meant in two glib hours. The story is set in July of 1964, when American military personnel in Vietnam were still classified as "advisers." Lancaster commands a detachment that is supported by Vietnamese troops and is dispatched first to secure and then to abandon a woebegone village called Muc Wa.

The title comes from an ancient Greek epitaph,credited by Barlett's to Simonides, and written for soldiers who fought another hopeless war: "Go tell the Spartans, thou who passest by, That here, obedient to their laws, we lie." In the film, the Americans see it carved in French at the gates to a graveyard for other strangers who had previously fought the losing battle in a strange land.

The film's struture is slightly askew: the first 15 minutes look like a stage play, with Lancaster interviewing new arrivals in his headquarters. Then from higher command come orders to secure Muc Wa, an outpost found to be deserted but later overrun with Viet Cong.

The crises of honor and dishonor that give the movie its point come about when some of the South Vietnamese troops are left stranded in the village as the enemy approaches and most of the Americans withdraw.

Mayes does some of the predictable Hollywood Liberal Breast Beating here, but in a fairly engrossing and halfway intelligent fashion he also dares to tussle with devastating moral ambiguities.

On the one hand, it's a pity that director Post wasn't either better equipped or more inclined to accentuate the subtler, nobler impulses in the script and cushion some of the garish and obvious touches. It all seems to pass in review before him while he nods acknowledgement.

On the other hand, this reticence to rev things up has kept the movie from going the hysterical route it might have gone in the clutches of a more grandiose and messianie commander in chief. "Spartans" works in the haunting, limited, mercurial way that "War Hunt," an underrated 1962 movie set during the Korean War, also worked. The filmmakers have gone after something more ellusive than a rhapsody of American guilt and the result deserves a certain respect.

Perhaps because "Company C" flopped so resoundingly, abeit so deserving, and because last year's war movies like "MacArthur" and "A Bridge Too Far" fell below box office expectations, "Spartans" is getting the softest possible sell from Avco Embassy Pictures. It's the kind of film that industrious audiences more or less have to discover for themselves.

It was probably Lancaster's name that got the picture financed in the first place - since Vietnam is considered a big downer in Hollywod, particularly with Francis Ford Coppola's "Apocalypse Now" undergoing so many costly delays that it might better be titled "Apocalypse on the Installment Plan." All of Lancaster's dialogue must have been rewritten into Lancasterese, or else the actor is able to turn anything into Lancasterse with his unmistakable and nearly selfparodistic rib-poking staccato.

It's hard not to think of every other movie Lancaster has ever made when he launches into such recitative as "Abraham Lincoln! How'd you like to go through life with a monicker like that, huh?"

As you watch this film, you long for Lancaster to get at least one more powerhouse warhouse role - this isn't quite it - that will really let him eat up the screen and spit it out again.

The young actors who make up the detachment include Marc Singer as the career-minded Capt. Olivetti and an especially effective Craig Wasson as the naively idealistic Cpl. Courcey. Audiences may note something naggingly familiar about one of the actors in a smaller role - John Megna as Cpl. Ackley. In 1962, Megna played Dill Harris, the little boy who visited Scout and Jem Finch in "To Kill a Mockingbird." He has grown up, and gone to war.