There's macho, there's military macho, and then there's the over-the-top machismo of the Marines. In the HBO miniseriesGeneration Kill, one character--a Marine--describes his branch of the military as "America's pitbull." The seven episodes ofGeneration Killfollow a battalion of Marines as they lead the invasion of Iraq, ultimately rolling into Baghdad itself by the last show. The language is dense with obscenities and military jargon, but it's surprisingly easy to follow, even if you don't study the glossary that comes in a booklet with the box set. What isn't so easy to distinguish are the characters themselves, except by surface details: This guy has a hoarse voice, this guy is an embedded journalist (a stand-in for Evan Wright, theRolling Stonereporter who wrote the book the series is based on), this guy is a white supremacist, this guy has a mustache, this guy is an officer obsessed with the other guy's mustache. The problem is that people are ultimately defined by what they do, and soldiers in war are all doing pretty much the same thing: Shooting, swearing, and sitting around as they wait to shoot and swear some more. ButGeneration Killisn't aiming for personal identification; the creators of the series (David Simon and Ed Burns, producers of the critically-adoredThe Wire) aim to immerse the viewer in the texture of the experience--which, in this case, is mostly chaos and confusion. Sandstorms are as great a threat as mortar fire; pizza trucks arrive out of nowhere on the brink of a mission (conveniently providing a bit of product placement); and the rules of engagement keep changing as the goals of the higher-ups grow increasing out-of-synch with the war on the ground.Generation Killcaptures the frustration and increasing cynicism of the grunt troops with vivid skill, as their simplistic morality--kill the bad guys!--grows more and more hollow.  Extras include some brief interviews with real Marines; the usual making-of documentary, mildly interesting but justly deleted scenes, and audio commentaries; and entertaining video diaries from Eric Ladin, the actor who plays the white supremacist.--Bret Fetzer