What is Thucydides's trap and how does it foretell the future of U.S.-China economic ties? Much has been said about China's strategic challenges to America. Less talked about is the financial tussle between the two. Harvard's Graham Allison walks Dan through his latest book and explains why a conflict is more likely than many people imagine. Along the way, Allison talks about North Korea and how dealing with a "nutty regime" fits into the broader competition between Washington and Beijing.