The opening credits montage and accompanying symphonic, guitar-strummed score that kick off "Lone Survivor" are unmistakably the work of writer-director Peter Berg (2012's "Battleship") and post-rock band Explosions in the Sky, sure to bring nostalgia to any fans of TV's underappreciated watermark drama "Friday Night Lights." As the film gets underway, its focus on the vérité-style interplay and camaraderie between a squad of Navy SEALs feels wholly natural and well within Berg's wheelhouse, each of them economically developed just enough that one settles almost instantly into their world. When the figurative rug is pulled out from under their feet and their situation becomes dire, then personally catastrophic, it stings all the more. As a war drama, "Lone Survivor" is brutal and unsparing. When the picture tries to become "important," it falls the way of maudlin pandering. Berg should have realized this story was vital on its own. Less would have been more.

On June 28, 2005, mission "Operation Red Wings" went into effect, sending a four-man recon team—Marcus Luttrell (Mark Wahlberg), Michael P. Murphy (Taylor Kitsch), Matthew Axelson (Ben Foster) and Danny Dietz (Emile Hirsch)—into the Hindu Kush mountains of Afghanistan to apprehend dead or alive Middle Eastern Taliban leader Ahmad Shah (Yousuf Azami). Upon getting dropped off, the guys are thrown an unexpected curveball when three villagers—an elderly man and two boys—stumble upon them. Faced with either killing virtual innocents or letting them go and being found out about, they honorably choose the fateful latter option. Now under attack and stranded with nowhere to hide, Luttrell and the rest of the team desperately attempt to contact Lieutenant Commander Erik S. Kristensen (Eric Bana) back at the operating base while fighting for their survival.

Based on the non-fiction book "Lone Survivor: The Eyewitness Account of Operation Redwing and the Lost Heroes of SEAL Team 10" by Marcus Luttrell and Patrick Robinson, "Lone Survivor" not only wades into spoiler territory with its very title, but the film goes one step further by starting at the end and then flashing back. Thus, even those unfamiliar with the true-life tale will know from the start that Luttrell will be the last man standing, badly injured and clinging to life. The meat of the story proper is nevertheless uncomfortably enthralling, an unflinching portrait of the sacrifices inherent in war and how quickly a person's hopes for the future—in fact, their very existence—can be snuffed out. Simultaneously, discussion is opened up about humanity in general, and the goodness and compassion that can arise when one least expects.

Berg makes sure that the bone-crushing, wound-splattering action following the first half-hour of setup will be felt by his audience. From multiple topples down rocky ravines to the ceaseless stalking which envelops them, this is not a film for the squeamish. Exploitation is avoided for the most part, save for the misguided editorial decision to bring slow-motion pomp and circumstance to the narrative's protagonists, while depicting the deaths of the Afghanis with a cold, abrupt detachment. This difference in shooting styles places a divide between them and, whether intentionally or not, transmits the wayward message that one life is more important than another just because he is on the side of the U.S.-born "good guys." Otherwise, these extended set-pieces of battle are close to astounding in the levels of tension and realism they ratchet.

Mark Wahlberg (2013's "Pain & Gain") earns top billing for the way the story plays out (and because said film is based on his actual counterpart's memoir), but there is no special focus on any of the four main guys. Each one is in the same perilous situation, and each one has his own experience and past to convey. Ben Foster (2013's "Ain't Them Bodies Saints"), Emile Hirsch (2013's "Prince Avalanche") and Taylor Kitsch (2012's "Savages") give intense, emotionally rattling performances as they stare down their own mortality and the idea of leaving their loved ones behind. Dietz's last vision—of the color swatch his wife had sent him for the painting of a room back home—is devastating in what it says so simply about our fallibility as creatures with only one life to live.

As masterfully shot and choreographed as "Lone Survivor" frequently is as a war-set thriller, director Peter Berg does not consistently make the right creative choices. In one scene in which Luttrell is captured, the Afghanis' discussion is subtitled—a cheat since there had been no subtitling of foreign languages up to this point and the story was being told from the SEALs' viewpoint. How much more involving yet scarily disorienting might this have been had it been left unexplained what was being said? Another issue: the climactic, quasi-existential voiceover is too flowery for what has come before it, detracting rather than contributing to the lingering effectiveness of all that had just been seen. The closing photographs of the real people are also a missed opportunity; by not pairing them with the actor playing them, it is difficult to decipher who is who. Many of these observations are small, but collectively they add up, lessening the lasting impact of the film even as it engages and disturbs. "Lone Survivor" is tough but hypnotic when it's good. When it's not, one can only watch as its potential for weightier greatness drifts away.