In a 2004 appearance at U.C. Berkeley, Errol Morris said his inspiration for the documentary derived from McNamara's book (with James G. Blight), "Wilson's Ghost: Reducing the Risk of Conflict, Killing, and Catastrophe in the 21st Century" (2001). Morris originally approached McNamara for an interview for an hour-long television special. That was extended multiple times and Morris decided to make a feature film. Morris interviewed McNamara for some twenty hours; the two-hour documentary comprises eleven lessons from "In Retrospect: The Tragedy and Lessons of Vietnam" (1995). He posits, discourses upon, and propounds the lessons in the interview that is "The Fog of War". Moreover, at the U.C. Berkeley event, McNamara disagreed with Morris's interpretations in "The Fog of War", yet, on completion, McNamara supplemented the original eleven lessons with an additional ten lessons; they are in "The Fog of War" DVD.