"Lone Survivor" is based on the memoir by Navy SEAL Marcus Luttrell, who provides an account of SEAL Team 10's mission in Afghanistan, Operation Redwing in June 2005. It was supposed to be a simple reconnaissance assignment, but things went awry, and the unyielding terrain didn't make things easier.

It took some time to slog through the first half of the book, which provided copious details about Navy SEAL tryouts, training, and culture. I was concerned that this meant the first half of the film would also be slow. Luckily, the training is quickly glossed over in the movie's opening credits, and we are introduced to the members of SEAL Team 10 — Matthew Axelson (Ben Foster), Danny Dietz (Emile Hirsch), Marcus Luttrell (Mark Wahlberg) and Michael Murphy (Taylor Kitsch) — who are already stationed at Bagram. We watch them bond, compete, hang out, and insult one another. It's bromance at its finest.

After a couple of false starts, the team finally gets the go-ahead for the mission. Based on the surveillance maps, the guys were uneasy about the mission because the terrain doesn't provide adequate cover. However, orders are orders, and these men are Navy SEALs, so hooyah, the show must go on. They're dropped into enemy territory, and they hike to a good observation point overlooking a Taliban village.

The first half of the film is necessary to set up the story and show the camaraderie between the guys, but it's a little slow, especially when the soldiers are marching in silence.

The movie picks up the pace when they're faced with a moral decision of what to do with a few goat herders who stumble upon their location. On the one hand, the herders haven't done anything wrong, and if the soldiers harm innocent civilians, the wrongdoing would be plastered all over the media. On the other hand, if they're set free, the herders could head down the hill and tell the Taliban about the American troops they'd encountered.

The soldiers decide to be good Samaritans.

That's when things go sideways.

The next hour is a series of harrowing firefights, injuries, visceral death scenes, and desperate attempts to get out of the hot zone. There are lots of scenes that elicited pained hisses from the screening audience, and although you know that Navy SEALs are tough, it boggles the mind to watch these men, riddled with multiple bullets, continue to put themselves in harm's way for their brothers in arms.

In the transition to the silver screen, the movie condenses some of the book's most gut-wrenching scenes and details. The story has the luxury, so to speak, of having so many unbelievable events that even when they're omitted, the remaining atrocities are still enough to keep you up at night. The skipped segments include Luttrell being so dehydrated that he can't open his mouth to radio the rescue helicopters hovering overhead, and his pants being literally blown off his body.

I had mentioned that "Act of Valor" possessed a certain gravitas because it starred active duty Navy SEALs instead of Hollywood actors, and I stand by that comment. However, the actors are all quite credible as Navy SEALs, and that's likely due to their intense workout regimens, and weapons and tactics training. It also doesn't hurt that director Peter Berg has a track record of employing military veterans on his film crews. (I don't know how well that served him in "Battleship," though.)

Wahlberg does an admirable job and has mastered the "crazy eyes" look, but as much as I try, I can't shake the sense that his most successful roles require him to be a modified version of himself.  Luttrell — the actual soldier and author of the memoir — is in a few scenes, and he is surprisingly relaxed and convincing on-screen, unlike his wooden brethren in "Act of Valor." (Sorry, guys.)

"Lone Survivor" had a limited release in December so it could be eligible for an Academy Award. We'll find out next week if that gamble paid off.  For those who haven't read the book, it's an excellent action movie, if a little slow to start. Those who have read the book will be happy to see that it's a faithful rendition. You may not be buoyantly happy at the end of the movie, but it's definitely worth seeing.

Score: 8.5/10

"Lone Survivor" is rated "R" and has a running time of 2 hours and 1 minute. It is showing in 2-D.