Defense Secretary Donald Rumsfeld is likely to face a difficult time marshaling support for one of his chief goals in the upcoming Quadrennial Defense Review: steering investments away from conventional weapon systems and toward capabilities needed to deal with new threats. The problem, according to Pentagon officials and defense analysts, is the Defense Department's computer models used to depict conflicts have not kept pace with the new threats -- irregular, catastrophic and disruptive -- that Rumsfeld wants the U.S. military...