What is D-Day? How the Normandy landings led to Germanys defeat in World War II | National & World [Video]

(CNN) — Friday marks 81 years since D-Day, the first day of the Normandy landings that laid the foundations for the Allied defeat of Nazi Germany in World War II.

The invasion – codenamed Operation Overlord – saw of tens of thousands of troops from countries including the United States, the United Kingdom and Canada landing on five stretches of the coastline of Normandy, France – codenamed Utah, Omaha, Gold, Juno and Sword beaches.

Planning for D-Day began more than a year in advance, and the Allies carried out substantial military deception to confuse the Germans as to when and where the invasion would take place.

When was D-Day?

The operation was originally scheduled to begin on June 5, 1944, when a full moon and low tides were expected to coincide with good weather, but storms forced a 24-hour delay. Allied divisions began landing on the five beaches at 6:30 a.m. on June 6.

What does D-Day …