There is still some explaining to do before we fully comprehend the revolution in Soviet foreign policy carried out by Gorbachev and his colleagues. Kull's book is a good place to start. He provides a thorough account of the vast reworking of ideas among the Soviet foreign policy elite during this period. For the most part he lets members of this elite, including the leadership, speak for themselves, quoting at length from their writings and, as a particularly helpful feature of the book, drawing on extensive interviews with them. One does not get from the book a profound and comprehensive explanation for this historic turn, but will certainly come away with a much richer sense of its intellectual side.