A penetrative and timely analysis of the postwar history of Communism, by Ulam (Director, Russian Research Center/Harvard; Dangerous Relations, 1983, etc.). Ulam provides fascinating new insights into the fissures within the Communist bloc and the motives for Soviet actions. He believes that it was the death of Stalin rather than any nuclear threats by Eisenhower that brought an end to the Korean War; that perestroika failed to appear in the 1950's largely because of China's belligerence and the reluctance of Stalin's successors to seem any less orthodox than the Chinese; that Mao's disastrous Great Leap may have been a crazy effort to teach the Russians the superiority of Chinese doctrine; that missiles were installed in Cuba not to defend Castro or to reverse the missile gap but to be used as a bargaining lever to get recognition for East Germany; and that the very mediocrity and lack of success of Gorbachev's early career as the Soviet minister in charge of agriculture may have led directly to his becoming the nation's leader after Chernenko's death, because the old men on the Politburo considered him no threat to them. Ulam does not add much to our understanding of the reasons for the collapse of Communism, and he may underestimate the effect of resolute Western action (as in NATO), but he offers substantial insight into why perestroika turned out to be not a new and better phase of Communism but its most decisive defeat. Ulam is no great stylist, but there are few historians with his background and grasp. A significant study.