The Normandy invasion, also known as D-Day, is considered the most decisive battle of the European Theater in World War II. "D-Day," a seemingly innocent and meaningless term at the time, appeared in military planning documents to keep German spies from becoming suspicious of Allied movements. The true name of the invasion was Operation Overlord. The culmination of nearly two years of planning, the invasion owed much of its success to the use of strategic deception.

A Bodyguard of Lies

The Allies knew that with more than 3,000 miles of German-occupied coastline from Norway to France, Germany was incapable of defending it all. The first part of the Allied strategy relied on two elaborate ruses; the first was designed to trick Hitler into believing that a joint attack of American, British and Russian forces would occur in Norway in the spring of 1944. The second ruse directed Hitler's attention toward the French port of Calais as the most likely location for an Allied invasion of France. These deceptions forced Hitler to shift troops away from Normandy, the invasion's actual planned entry point.

Elaborate Deception

Only 22 miles of water separate the British town of Dover from Calais. Because it is the shortest distance between the two countries, it seemed the most likely site of an Allied invasion. The Allies capitalized on this assumption. General Dwight D. Eisenhower's staff created a fictional group of 50 divisions supposedly massing in England. Construction crews built seemingly huge installations from plywood and canvas with inflatable tanks and other vehicles stationed around them. In the weeks immediately prior to the invasion, the Allies bombed the Calais area more than any other French location to keep German attention focused there, while the Allies prepared for the actual invasion farther south in Normandy.

Airborne Assault

On June 6, 1944, just after midnight, the Allied invasion began. Thousands of British and American airborne soldiers parachuted behind enemy lines with the task of seizing or destroying roads and bridges to the coastal area. This strategy would isolate the Normandy beaches and the few German forces guarding them, as well as prevent Germany from sending reinforcements once the invasion commenced in earnest. Allied planes also dropped parachutist dummies wired with firecrackers that detonated when they landed. The noise not only drew German troops away from the landing sites of actual paratroopers, but also away from the beaches where the invading forces would land after dawn.

Breaching the Beaches

The overall Allied strategic goal was to penetrate France by overwhelming a weak spot in Germany's defenses with more force than the enemy could repel, and create artificial harbors able to continually reinforce and supply invading troops without the need to capture an existing port. For the invasion, the Allies assembled nearly 5,000 warships, transports and other vessels -- the largest naval armada in history. The Allied amphibious assault was prefaced by steady bombardment of the Normandy beaches from air and sea. Bombers flew more than 11,000 sorties. During the initial hours of the amphibious assault, more than 100,000 Allied soldiers were landed. The invasion put Germany on the defensive, ultimately leading to the liberation of France and Allied victory in Western Europe.