The document provides background information on D-Day and the Normandy landings during World War 2. It discusses the Allied armies that participated in the invasion including the US, UK, Canada and others. It describes Operation Overlord which was the code name for the Battle of Normandy, and details the causes of the landings, those responsible for planning and leading the operation, the number of troops and casualties involved, and the Allied strategy and defenses employed by Axis forces. The summary concludes with the results and consequences of D-Day, which marked a major turning point in the liberation of Europe from Nazi occupation.