American participation in World War II was a major component of the Allied invasion. As a result, the United States faced significant challenges during the long build-up to D-Day.
Among them was the appointment of Dwight Eisenhower as Supreme Allied Commander for the invasion. Despite his best intentions, Eisenhower had to work with many difficult personalities, including President Franklin D. Roosevelt and Prime Minister Winston Churchill.

How It Happened
The D-Day landings were one of the great turning points of 20th-century history. They helped establish a base in Nazi-occupied France and liberate Europe from the Nazi regime.
To prepare for the invasion, a major naval and aerial bombardment was launched against German defenses on the Channel coast of France and the Low Countries. This preparation was followed by deception tactics, which led the Germans to believe the invasion would be further along the coastline.
As part of Operation Overlord, Allied forces landed on five beaches of Normandy in Nazi-occupied France. These were codenamed from east to west: Sword, Juno, Gold, Omaha and Utah.
Allied troops landed at each beach at around 6:30 a.m. and were greeted by heavy German fire. Many were ill during the long journey to shore and suffered hours of seasickness. They then began clearing mines and obstacles from the beaches. They were aided by their superior air power, which was much more powerful than that of the Germans.
The Preparation
America was to play a key role in the invasion. Its leaders had to overcome a host of challenges including political, cultural and personal differences.
Before the invasion, the American military leadership set up a special combined operations bureau known as COSSAC. This new command would design and execute the amphibious operation.
The planning for D-Day was complex and a great deal of research was undertaken into the strategic and geographical aspects of the invasion. This included the beaches, moon phases and tidal ranges, sites of airfields and sailing distances from channel ports.
During this time, two artificial harbours were built, nicknamed Mulberry Harbours, for the transport of troops and equipment across the Channel. In addition, many camps and depots were arranged along the south coast of England to house troops and equipment.
In the days leading up to the attack, false radio traffic, dummy landing craft and vehicles and double agents were created to deceive German soldiers. This was known as Operation Fortitude.
The Landings
Allied leaders agreed that the United Kingdom, France, and Canada needed to land troops on mainland Europe in order to liberate Nazi-occupied territory. This massive cross-Channel attack, codenamed Operation Overlord, began on 6 June 1944.
The landings, often called D-Day by the Americans, were one of the most significant events in the Second World War and laid the foundations for Allied victory. Despite challenges and fierce enemy opposition, Allied forces persevered in establishing a beachhead in Normandy.
Before the onset of Operation Overlord, American planners studied the lessons learned during previous amphibious operations. This study helped to prepare a successful crossing of the Channel and to ensure that Allied troops would be well-supplied for their subsequent campaigns.
The Invasion
The invasion of Normandy Landings was the key part of the Allied plan to take back Europe from Nazi Germany. It was a turning point in World War II, and it paved the way for the liberation of France.
When considering where to attack, many strategic and geographical characteristics were taken into consideration. One important factor was the strength of German defences at certain crucial points.
To combat these, naval forces took part in 'Neptune' and carried out bombardments of German coastal defenses before and during the invasion. This helped to bolster the invasion force's morale and ensure they landed on the beaches safely.
The US Army was responsible for the western part of the invasion, landing on Utah and Omaha beaches, whilst the British and Canadians were involved in the eastern part, landing on Gold, Juno and Sword beaches. Each beach was heavily defended, with heavy gun emplacements overlooking the beaches and mined shorelines that were difficult to clear.