This is an updated edition of the now-classic original of the same title. It has three new substantial chapters: a prologue, a chapter on new evidence on World War I, and an epilogue. The updated edition contains the now-famous typology of international crisis, the original critique of deterrence, the emphasis on agency, and the turn to political psychology to explain sharp departures from rational policy-making. The new chapters update and reevaluate these arguments and approach a critical hindsight assessment in light of post-Cold War developments.