The Allies made massive preparation in late 1943 and early 1944. There was a huge buildup of Allied forces in southern England. To distract the Axis, a fake army buildup was staged. This task fell to Lieutenant General George Patton. He was pulled from command of his troops in Italy and set in command of this imaginary army. This army consisted of inflatable tanks and troop carriers and empty tents. Another decoy the Allies made was that they leaked false information that led Hitler to believe that the invasion would take place in Norway, hundreds of miles away from Normandy. Because of this, Hitler massed a number of his forces there in preparation for this false landing.
The real invasion would happen in several stages. First, Allied bombers would fly thousands of sorties over the invasion area. Second, troops would be loaded on their transports and begin the journey across the channel. Third, Allied paratroopers would board their transports and fly to their drop zones and drop behind the Atlantic Wall. These airborne units would disable German artillery emplacements and disable the ability for the Axis to reinforce themselves for several hours, and link up with the landing armies on the beachheads. Fourth, the beach landings would take place. 35,000 soldiers would storm the coast of Normandy on five different beaches. From West to East they are: Utah, Omaha, Gold, Juno, and Sword. The American VII Corps would come ashore at Utah, and V Corps would land at Omaha. The British were assigned to the latter of the five beaches. They would land their XXX Corps at Gold, I Corps at Juno and Sword beaches. These forces would link up with each other and the paratroopers inland to make one giant beachhead. The invasion was originally planned for the morning of June 5th, but it was postponed a day due to stormy weather over the English Channel.
The invasion began at midnight June 6th when the first Allied paratroop drops and glider landings occurred in Normandy.