University of Virginia historian Philip Zelikow says President Woodrow Wilson made the most consequential diplomatic error in U.S. history. In his new book, "The Road Less Traveled," Zelikow presents compelling evidence that Wilson could have avoided getting the U.S. involved in the First World War and brought the conflict to a negotiated end in 1916 in the process. The peace ball was in his hands, but he fumbled it. This reassessment of a critical chapter in history holds important lessons for a world troubled by enormous problems that require international cooperation.