The great actors of history cannot be neatly tucked between the covers of a book and filed away like so many pressed botanical specimens. Their actions cannot be explained according to a specific timetable like the coming and going of so many trains. Although scholars may designate the beginning and ending of an era with exact precision, great historical events, particularly those that erupt suddenly and violently, build up slowly, and, once having begun, never end. Their effects linger long after the action faded from view. Like the tingling vibrations of a bell that we can still sense well after it has stopped ringing, Genghis Khan has long passed from the scene, but his influence continues to reverberate through our time.