Beckham
Beckham is a local kid who hawks DVDs outside of the U.S. base. Will takes a shine to Becks, apparently amused by the boy's benignly aggressive sales techniques and the bizarre—and often pornographic—stable of English phrases he uses to catch the attention of soldiers as they walk by.
At first, the relationship between Will and Beckham plays as a bright spot in a film that's otherwise focused on how crummy and unpredictable war is—and that portrays Baghdad's communities as a constant potential danger to the U.S. forces. From the moment Thompson gets blown up by a civilian (or someone they all thought was a civilian) in the first scene, we get the message loud and clear: the EOD team is constantly on guard against the locals surrounding them, who may or may not be radicalized or otherwise out to get them.
However, Beckham is an exception, and Will really seems to enjoy joking around with him. The two even have an impromptu soccer session at one point. Through these interactions, Beckham becomes the one Iraqi character who gets any kind of real air time or characterization—probably because he's the only one our main character ever thinks deeply about.
That warm-and-fuzzy bromance takes a dark turn, though, when Will and his team find the body of a kid who's been used as a body bomb. We the audience can't really see the kid's face, but Will is absolutely convinced it's Beckham. As a result, he's unwilling to follow the team's initial plan of evacuating and then blowing up the whole place, the boy's body included, to destroy a bomb lab and neutralize the threat of explosion.
Will's decision is super risky and involves the disgusting task of opening the sutures in the boy's body and reaching within to grab and disarm the bomb. Understandably, he's very emotional about the whole unpleasant operation, but he gets through it and then removes the boy's body from the building before it's destroyed.
Is He or Isn't He?
Here's the thing, though: Will's fellow soldiers aren't sure the kid is Beckham:
ELDRIDGE: You think it's that little base rat?
SANBORN: No, I don't.
ELDRIDGE: You positive?
SANBORN: Sure. Hey, I don't know, man. They all look the same, right?
ELDRIDGE: I don't know. Will seemed sure. That was weird.
SANBORN: Very weird.
There's lots going on in that dialogue. First of all, there's the bombshell (pardon the pun) that the boy might not be Beckham. Then, there's the more troubling suggestion that the faces of the Iraqi people are so interchangeable that Will could make that mistake in the first place and Sanborn could say that they all look the same. Sure, the kid's face is covered with blood, but it's still super odd.
Then, of course, there's the casual way Sanborn kind of dismisses the whole question of whether the boy is Beckham ("Sure. Hey, I don't know, man.")—like they're taking guesses about who will win the Super Bowl.
Anyway, the discovery of "Beckham's" body really throws Will off balance. He even ends up going on an ill-advised adventure off the base to try to find the people responsible for the boy's death. Sure, Will has always been a risk-taker, but in that whole series of events, he seems completely unhinged—his emotions have totally taken over his grasp of reality.
Of course, it turns out that the boy with the bomb was not Beckham, and Will went through all that emotional angst for a boy he didn't know. Will is actually angry when he sees Beckham alive and selling outside the base again.
We could read the whole incident with the body bomb as symbolic of how faceless the Iraqis are in the eyes of the U.S. forces—since clearly, at least to some extent, they are. Sanborn and Will both seem to have trouble identifying a kid they've been seeing every day.
However, we could also come up with a more charitable interpretation of the whole incident. Maybe Will doesn't really question whether the kid is Beckham at first because the fact is that it could easily be him. The people affected by this war he's fighting suddenly have names attached, and it's that fact that sends Will into a tailspin, convinced that he's lost his buddy.
Either way, Beckham embodies the humanity that Will and his fellow soldiers largely ignore in the Iraqi people that surround them. When Will is forced to confront that humanity, it's super, super traumatic for him.