The war in Vietnam marked a watershed in American domestic politics: bitter division over the goals and methods of the American war effort intersected with the civil rights movement, questioning of traditional social values, and the ubiquitous rise of broadcast television which brought these issues into American homes each evening, resulting in a widespread loss of faith in institutions and government among Americans. While this narrative has become conventional wisdom in American history, this week's guest, Mark Lawrence, argues in his new book, The End of Ambition: The United States and the Third World in the Vietnam Era, that the war in Vietnam marked dramatic re-thinking of ambitions in U.S. foreign policy, as well. Lawrence tracks the arc of American involvement abroad from the idealism of the Kennedy administration, through the pragmatic deal-making of the Johnson administration, to the cynical realism of the Nixon administration. Lawrence traces as well, how this development was paralleled by the rise of leaders in the developing world whose idealism was tempered with pragmatism and, at times, radicalism.  Lawrence's book is a fascinating biography of modern American foreign policy in its formative years.