The attacks of 9/11 reminded us of humans’ seemingly inexhaustible imagination and capacity to kill innocent lives. What was unthinkable one day, became reality the next. Today, in the back of everyone’s mind lies the irrepressible fear that one day, terrorists will orchestrate an attack that would make 9/11 look like a Saturday night brawl. What would happen if Al Qaeda dropped a nuclear warhead on Chicago or New York City and kill a million people? How would the US retaliate?