“It’s one of the best things I’ve ever done,” Paul Greengrass says of the frenzied nine-minute action sequence at the heart of his Iraq thriller, Green Zone. That’s quite a statement, coming from the director of four much-imitated, quick-zooming, rapid-fire films — Bloody Sunday, The Bourne Supremacy, The Bourne Ultimatum, and United 93 — that revolutionized the way realistic action is shot. So here’s the setup: Matt Damon plays Miller, an officer whose WMD-hunting task force is pointlessly digging in a dirt soccer field. As the team digs, he interrogates a Baathist, and is on the verge of a breakthrough when rival Special Forces officer Briggs (Jason Isaacs) suddenly lands a helicopter, takes the prisoner, and beats down Miller. Watch the scene, and then follow the slideshow in this post as Greengrass explains the choices behind every shot.