"George W. Bush waged preventive war in Iraq regarding (nonexistent) weapons of mass destruction. Obama is waging preventive war in Afghanistan to prevent it from again becoming "a staging platform for terrorists," which Somalia, Yemen or other sovereignty near-vacuums also could become. To prevent the "staging platform" scenario, U.S. forces might have to be engaged in Afghanistan for decades before its government can prevent that by
itself." (thanks Nabeel)