That's the point: We don't know what's next. But the four young Marines leading me through the Night Integrated Training Environment (Nite) at the Marine Corps Warfighting Laboratory in Quantico, Virginia, must learn to figure it out. They're training for the Marine Corps' specialty: night combat in environments peppered with alarmed civilians, explosive booby traps and enemy soldiers--not unlike what's facing their fellow Marines in Iraq at this very moment. And at the Nite, they get it all. This 10,000-square-foot facility, the only complex of its kind operated by the U.S. military, features a sequence of rooms, often rigged with simulated machine-gun-firing combatants, that mimic deserts, jungles, woodlands and dense urban terrain. Training exercises are held day or night, in any weather, with any variable the Marines choose. Right now an illegal drug lab, a radio hut, a school bus, a treehouse, dry riverbeds, wire fences, log piles and a number of other obstacles are arranged in a course that would prove challenging even in broad daylight.