In taking office in 2001, the Bush administration moved quickly to deliver on its campaign promise to build a missile defense system to protect the US from attack. For the administration and its supporters, such a defense was a rational (if not moral) response to fledgling nuclear adversariesespecially Iran, North Korea, and Iraq (before 2003)—that eschew traditional rules of restraint and possess small arsenals against which the US could credibly defend. Of course, the September events of that year forced a profound redirection in US policy away from planning against an adversary, with a fixed base of operations, that would adopt the “traditional” Cold War-style of attack-firing missiles over intercontinental distances against US targets-to a geographically dispersed adversary that could sneak into the US and deliver its blows through any number of creatively destructive means. But the case for missile defense is only strengthened, proponents argue, by the horrific terrorist attack on the World Trade Center in New York, which proves once and for all that the US faces a new nemesis, one that will go anywhere and do anything to accomplish its goals.