In the middle of a heated battle between child soldiers, where guns are made from sticks but the explosions are real, a determined young fighter has a momentary lapse in concentration. He looks to his left to see a female friend completely immersed in the war, and for a split second feels intense fear - the thought that he might lose her here today.
Yet Lord of the Flies allusions aside, kids aren't actually blowing themselves up in backyards across America (though they might be in Palestine, Iraq...). When the final scene reveals a grown man shot by actual bullets, we understand that all that has passed before was a memory of a childhood game. In his mind the reality of his current situation is belied by thoughts of an earlier, more innocent time. This soldier remembers that moment of fear in the forest - perhaps his earliest hint of love - and now realizes that he has indeed lost her (and his youth) forever.
Despite the sticks and stones which define the game, the director includes very realistic emotions and violence in the proceedings to make a direct correlation between childhood experience and adult consequences. We are all veterans of those tumultuous years spent growing up, and we carry the scars of the socialization that occured. It isn't just that we are trained from youth to see life as a two-sided struggle where violence is a neccesity, but our confrontational perception carries over to matters of the heart as well. As the band sings of a pained relationship, the camera displays love as a battlefield - where someone is always bound to get hurt.
At the same time it seems the man in the final shot is killed wearing American gear in the desert, and thus likely a victim of the current war in Iraq. By comparison the earlier scenes of violence take place guerilla style in the jungle, which could very well represent Vietnam (there are a few Platoon-esque shots as well). The lesson here being that certain people may have never learned their lesson, and when that happens history is bound to repeat itself.