We call it 9/11 now, the day that brought the future crashing into us. Suddenly we are facing a new kind of warfare, a hidden enemy willing to strike anywhere, targeting civilians, using terror as its greatest weapon. The U.S. has the most powerful war machine the world has ever seen. But it was created to combat conventional forces, and now the military is rapidly shifting to face a new kind of danger that once seemed unimaginable. Whether it is in Iraq or against the shifting cloud of terrorism, American troops are now being challenged as never before. This is the story of what they’re facing.