The Longest Day is a 1959 book by Cornelius Ryan telling the story of D-Day, the first day of the World War II invasion of Normandy. It details the "coup de main" operation by gliderborne troops, which captured the Caen canal and Orne river bridges (Pegasus Bridge and Horsa Bridge) before the main assault on the Normandy beaches. It sold tens of millions of copies in eighteen different languages. It is based on interviews with a cross-section of participants, including U.S., Canadian, British, French and German officers and civilians.