“Border Post,” Rajko Grlic’s 2006 film which opens today at the Pioneer, is credited as a “Croatia/Bosnia and Herzegovina / Macedonia / Slovenia / Serbia / Hungary / Austria / France” co-production. The film is, in fact, a period piece taking place just a few years before many of those Balkan credits would be possible or necessary. As “Border Post” opens, it’s 1987 on the Yugoslavian-Albanian frontier. Civil War is still four years away and in the soon-to-be-former Social Federal Republic of Yugoslavia, it’s Cold War business as usual.

At a small mountainside garrison, a group of bored and horny Yugoslav troops serve out their mandatory military service by doing as little work as they can get away with short of running afoul of their careerist superiors. By day, the soldiers mark time in unenthusiastic drills and by surreptitiously smoking hashish “courtesy of our unaligned Afghan brothers.” By night they empty any bottles and chase any skirts that they can find in a nearby town.

Sinisia (Toni Gojanovic) is a young doctor quietly riding out a tour of duty before returning to his native Dalmatia. His friend Ljuba (Sergej Trifunovic), however, takes perverse amusement in waging an undeclared psychological war with the unit’s martinet party member commander, Lieutenant Pasic (Emir Hadzihafizbegovic). When Sinisia is summoned to the Comrade Lieutenant’s office for a private medical consultation, he discovers that at least as far as recreation is concerned, the officer and his men are on the same page.

Sinisia’s diagnosis confirms that married lieutenant Pasic has contracted syphilis. A clean bill of health will require three weeks of penicillin treatments. But the lieutenant is scheduled for a conjugal furlough in just a few days. To ensure that neither his spouse nor his superiors learn of his indiscretion, the lieutenant uses his command as a personal smoke screen.

“Comrades!” Lieutenant Pasic tells his troops, only half exaggerating, “The situation is becoming unexpectedly complicated here.” Rather than face his wife with the truth, Pasic informs his superiors that their Albanian rivals across the border are massing for an attack. All leaves are canceled until the crisis is over. Under the circumstances, a commanding officer would be derelict in his duty were he to leave his post, so Pasic sends Sinisia down the mountain to reassure his wife Mirjana (Verica Nedeska) that her gallant husband will be home just as soon as the threat is passed — about three weeks hence.

Lonely, smart, and wise to the ways of the career soldier’s world, Mirjana finds herself drawn to the messenger even if his message is suspect. The attraction is clearly mutual, but as Sinisia and Mirjana’s passion grows and the lies combine and compound, it’s also clear that somebody’s going to get hurt. And with all those guns and bayonets on hand, it’s probably going to involve considerably more than just tears.

Adapted from a novel by the Croatian journalist Ante Tomic, “Border Post” nimbly walks the line between farce and drama for most of its 94 minutes. Mr. Grlic, who also co-wrote the film, smartly uses period background broadcasts to color his portrait of a nation sputtering toward civil war on ideological fumes. By 1987, Yugoslavian strongman Marshal Tito had been dead for seven years. Yet state-owned television announcers on a barracks TV set soberly describe an ongoing cross-country relay race to celebrate the late dictator’s birthday and an academic symposium about the country’s future entitled “After Tito: Tito.”

The personal ironies of “Border Post” are what really distinguish the film from any number of other military black comedies. “Everything will be fine,” Sinisia tells Verica during a momentary lull in their ardor. “No, it won’t,” she replies matter-of-factly. “Nothing will be fine.” She knows that Sinisia is at once too innocent and too arrogant to offer her the marriage she’s been unable to have with the lieutenant. Nevertheless she offers her heart to the young man and in doing so inches ever closer to tragedy. Meanwhile, Lieutenant Pasic knows on some level that he himself is far too detestable a character for Ljuba to befriend. And yet when Ljuba suddenly starts toeing the party line, Pasic needs so badly to believe that his mission is just, that he plays along until it’s too late.

In its hasty climax, “Border Camp” goes from bawdy to bloody in just a few broad plot strokes. Full of sudden changes of heart, acts of martyrdom, and resolves to action, the film’s final 15 minutes rub against the smooth, cynical grain of what’s come before. But it’s a tribute to the quality of the performances (especially Ms. Nedska’s Mirjana) and Mr. Grlic’s uncluttered direction, that the film’s abruptly tragic ending doesn’t dull the sting of the film’s finely honed satire.

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