c-span: by the way, you say you don't agree entirely with "the longest day," cornelius ryan's book. what are the differences in what you've found? >> guest: first of all, ryan didn't have access to anything like the number of sources that i did. ryan interviewed 250 men. c-span: when did he write that book? >> guest: in 1955-57. ryan didn't know about the ultra secret, for example. there is an awful lot of high command stuff that ryan never knew about. i'm not knocking ryan's book. it was an inspiration to me. i read it when it first came out. i saw the movie, like everybody else in this country, and i loved the movie. c-span: he's dead. >> guest: yes. c-span: and what was the ultra secret? >> guest: the ultra secret was the breaking of the german enigma code. the germans had this fabulous encoding system which they thought was the best in the world, and they were right. it was. they also thought it was unbreakable, and they were wrong about that. ryan didn't know that we knew so much about the germans. the biggest disagreement that i have with ryan -- it's not a disagreement; it's w

all these surprises on what happened and found out that what ike had thought had happened, what cornelius ryan had thought had happened, what zanuck thought had happened wasn't what happened. c-span: where did you do this? >> guest: i have a cabin in northernmost wisconsin that i go to in the summers where i do almost all of my writing, and i just sat there and did it. c-span: why did you pick that spot to do it? >> guest: it's been in our family for -- i've spent at least a part of every summer of my life there. my grandfather purchased -- it's 20 acres with a small lake. my grandfather was in the corps of engineers in 1938, so he had a salary, and this place came up for sale for the back taxes, $161. he bought it, and he built this log cabin, and it's now become mine and it's where i go in the summer. c-span: can you write anywhere else? >> guest: sure. i have an office in bay st. louis where i live during the fall and winter. one book i started -- i did a book called "pegasus bridge," which was the action that opened this d-day, and i spent a month in britain interviewing the survivors of t