From World War I to the wars in Iraq and Afghanistan, conflict has long been a part of American history. These events have molded society and culture,  producing effects that ripple through generations. 

Author and historian Margaret MacMillan joins Julian Zelizer and Sam Wang in this week's episode to discuss how war is in our bones. She is author of the new book, “War: How Conflict Shaped Us" and a professor of history at the University of Toronto and emeritus professor of international history and the former Warden of St. Antony's College at the University of Oxford.