This book starts with the question of what conditions make North Korea choose between confrontation and collaboration toward the United States. In order to answer the question, we examine the five cases related to Pyongyang's nuclear and missile diplomacy with the U.S. from 1992 to 2002, employing prospect theory combined with human needs theory. Our findings include: (1) North Korea employs brinkmanship strategy when its security is threatened; (2) it takes a conflictual policy when its identity is threatened; and (3) Pyongyang becomes cooperative when it perceives its security to be improving. The findings of the book recommend policy makers who want to see Pyongyang cooperate with the world as follows: (1) to alleviate Pyongyang's security concern; (2) to provide them with humanitarian assistance to relieve their domestic insecurity; and (3) to consider how to satisfy their identity need when dealing with the country.