Director Paul Katis used mostly unknown actors, such as Jon-Paul Bell, left, and Malachi Kirby, in “Kilo Two Bravo.” (Honora Films/Kajaki Film Ltd.)

First-time feature director Paul Katis uses the economical production values of his British war film “Kilo Two Bravo” to his advantage, finding reserves of suspense, humor and even grace in the spare yet harrowing situation he creates. Few war films are entertaining in a traditional sense. This one is so relentless that recoiling from it is nearly impossible.

Inspired by a true story, the tale of soldiers stationed near the Kajaki Dam in Afghanistan opens with a serene underwater shot, taken near the dam. Featuring a figure floating in a bright blue matrix, the scene makes for a jarring visual contrast with the harsh yellows of the surrounding landscape. Katis uses unknown actors as the soldiers, creating a sense of camaraderie that draws attention to the overall morale of the group, and away from any single individual. Screenwriter Tom Williams’s dialogue, spoken with thick English accents, is at times impenetrable, yet is easy enough to understand when it matters.

While on a routine patrol, one member of the small group accidentally steps on a landmine, losing his leg. Foolishly, the rest of the men rush to his aid, only to realize that the valley is full of mines. More of them explode, leaving the men in varying degrees of pain and shock, and overwhelming the squad’s lone medic. With morphine and water running low, each attempt at medical care leads to another disaster.

Katis films this with unflinching realism. In addition to the men’s screams of agony, the makeup effects are disturbing. We’re shown viscera and dangerous-looking internal injuries. In one intense scene, a soldier with a collapsed lung begs his friend to stab him with a long needle so that he doesn’t suffocate. Pushed past common sense, the medic hops through the minefield to help as many men as he can, flinching every time he lands safely. Yet the filmmakers aren’t interested in exploitation. Instead, “Kilo Two Bravo” unfolds like a war procedural. Practical problem-solving, not heroics, will save these men.

During long periods of inaction, the men talk, veering between moments of desperate levity and outright despair. When one soldier grumbles that it’s his birthday, all the lads muster a pathetic yet hilarious rendition of “Happy Birthday.” A modern manifestation of the English “stiff upper lip,” the tale is dampened by a sneaky political message: Since the minefield is a relic from the war between the Afghans and Soviets, “Kilo Two Bravo” is a brutal reminder of what it means when the war machines of an earlier generation are left behind to be cleaned up by the next.

Zilberman is a freelance writer.

R. At AMC Hoffman Center 22. Also available on demand. Contains coarse language and violence, including horrific war injuries. 108 minutes.