How did it happen that the United States and the Soviet Union managed to get through more than four decades of Cold War confrontation without going to war with one another? Historian John Lewis Gaddis suggests an answer to this and other questions about post-war diplomacy. Gaddis uses declassified American and British documents to explore several key issues in Cold War history that remain unresolved: precisely what it was about the Soviet Union's behaviour after World War II that American leaders found so threatening; whether the United States really wanted a sphere of influence in post-war Europe; and what led the Truman administration first to endorse, but then immediately avoid American military involvement on the mainland of Asia.