The Sino-Soviet split in the 1960s was one of the most significant events of the Cold War. Why did the Sino-Soviet alliance, hailed by its creators as "unbreakable", "eternal", and as representing "brotherly solidarity", break up? Why did their relations eventually evolve into open hostility and military confrontation? With the publication of several works on the subject in the past decade, we are now in a better position to understand and explain the origins of the Sino-Soviet split. But at the same time new questions and puzzles have also emerged. The scholarly debate on this issue is still fierce. This book, the result of extensive research on declassified documents at the Chinese Foreign Ministry, and on numerous other new Chinese materials, sheds new light on the problem and makes a significant contribution to the debate. More than simply an empirical case study, by theorising the concept of the ideological dilemma, Mingjiang Li's book attempts to address the relationship between ideology and foreign policy and discusses such pressing questions as why it is that an ideology can sometimes effectively dictate foreign policy, whilst at other times exercises almost no significant influence at all. This book will be of essential reading to anyone interested in Chinese-Soviet history, Cold War history, International Relations and the theory of ideology.