A platoon of National Guardsmen are sent to the Louisiana swamplands on weekend manoeuvres, and split into squads. One of them is led by Sergeant Poole (Peter Coyote), a tough but fair military man who is joined by a new recruit from Texas, Corporal Hardin (Powers Boothe) who he warns he doesn't want any trouble. However, it's not Hardin that will be the source of their problems as the men fire off their blank rounds and look forward to meeting up with a group of prostitutes at the end of their mission; this reward has been set up by the patrol's resident smartass, PFC Spencer (Keith Carradine). And as they venture into the forests, they find themselves quickly out of their depth...
Early on in the ironically-titled Southern Comfort, under the opening credits in fact, there's a scene of Fred Ward's Corporal Reece tripping on a fishing net left by a trapper. Instead of stepping over it, he lifts it out of the water and cuts it in half, thereby demonstrating the squad's fatal disregard for their environment and the locals. Director Walter Hill co-wrote the script with Michael Kane and David Giler and you can see right away, as many did, the parallels they were reaching for. This is a Vietnam War allegory, with the soldiers here plainly representing cocky and flawed America overconfident in thinking it could win out against an apparently unprepared enemy.
Of course, it's the troops who prove themselves unprepared - for a start, their map is inaccurate and they now have a river to cross that they hadn't planned on. It so happens that Reece stumbles across three canoes and persuades his fellows to take, i.e. steal, them although one conscience-stricken soldier leaves a note for the trappers they belong to. They're barely halfway across the river when the owners appear from the trees, but the guardsmen are unsure whether these Cajuns speak English, not that it matters when the prank-pulling PFC Stuckey (Lewis Smith) fires blanks in their general direction.
The Cajun's response? Well, they weren't to know that they weren't in any danger, so they blow the top of the Sergeant's head off and here the screws begin to tighten with a finely honed tension that never lets up. The squad fall into the water, struggle to the bank and debate what to do next now that they are without a leader. Sergeant Casper (Les Lannom) is a weak replacement for Poole, but installs himself as head of the group in spite of nobody taking him seriously. In a sense, the film is a deconstruction of masculine attitudes as these remaining men all try to bluff their way through a desperate situation by employing their aggression and trying to out-macho each other.
None of that is successful, as they are not only at the mercy of the swamplands, but the hunters too and the little-seen Cajuns become part of the scenery, an elemental force that can just as easily fell trees on the heads of their prey as pick them off with shotguns. There is one Cajun that the soldiers get to know when they uncover trapper Brion James (perfectly cast) at his hut and accuse him of killing Poole, no matter that they have no evidence. The growing paranoia sends Corporal Bowden (Alan Autry) round the bend and he blows up the trapper's home, just another example of the way the soldiers sabotage themselves. If anything, the echoes of Vietnam are too overt, as the characters are more symbolic than living people, although Carradine and Boothe are consistently excellent. Playing out like a horror movie, you don't know who will survive or what will be left of them, and Southern Comfort doles out the thrills with ruthless efficiency. Evocative score by Ry Cooder.