One notion involves a scenario quite literally torn from the pages of a science fiction novel, in which a virtual training system becomes the actual means of waging war. "Ender's Game," a cult classic by Orson Scott Card, tells the story of a group of young soldiers battling aliens in a video game. In the end, they emerge to find that their victory has saved humankind, and that it was not a game.

" 'Ender's Game' has had a lot of influence on our thinking," said Michael Macedonia, director of the Army's simulation technology center in Orlando, Fla., which plans to build a virtual Afghanistan that could host hundreds of thousands of networked computers. "The intent is to build a simulation that allows people to play in that world for months or years, participate in different types of roles and see consequences of their decisions."