Based on Anthony Swofford's memoir, this is the story of a group of Marines sent to Saudi Arabia as part of the buildup to Operation Desert Storm -- the first Gulf War. They've been trained to fight and kill; Swofford is a scout/sniper. But their mission consists of guarding Saudi oil fields that aren't currently under attack; it will be six months before American soldiers actually get involved in the Iraq-Kuwait conflict, and when they do, the war will last for only four days.
So Jarhead is about the frustration that comes about when there isn't much happening, which is potentially a deadly subject for a movie; if nothing's happening, how do you hold the audience's interest? It's easier in a book, where the author can tell us what he's thinking, but converting a story about internal emotional states to the screen isn't easy. Director Mendes and screenwriter William Broyles Jr. don't quite pull it off.
Jake Gyllenhaal plays Swofford, and the movie is told from his point of view, with the result that this is an even more anonymous group of soldiers than we usually get in war movies; Swofford doesn't get to know any of them very well, so neither do we. The exception is Peter Sarsgaard, who plays Troy, Swofford's sniper-team partner; he gives a fine, subtle performance as a man gradually collapsing under the stress of inactivity and the desire to see combat.
The other major role in the movie is the unit's commander, Staff Sergeant Sykes, played by Jamie Foxx, who displays a maturity and gravitas unlike his previous work. Dennis Haysbert makes a nice impression in a two-scene cameo performance that makes me wish someone would cast him in a comedy. (Which isn't to say that his scenes are funny, exactly -- the second isn't at all -- but there's something about his timing that makes me think he could be hilarious if someone found the right way to use his size and deep, booming voice.)
But Gyllenhaal is at the center of the movie. The screenplay doesn't give him any of the usual devices to communicate his feelings verbally -- there are no letters home, there's only a small amount of voice-over narration, and Marines aren't encouraged to share their problems with one another -- and Gyllenhaal doesn't manage to get them across non-verbally. It's a very blank performance, and Swofford, despite being the movie's central character, blurs into the group of anonymous soldiers. I kept wanting Sarsgaard to come back and give the movie a jolt of energy.