The+Invasion's+Beginning

 **The Planning Phase**
 * Originally planned for May 1, 1944, the invasion date was set for dawn on one of three days—June 4, 5, or 6. Imperative that a combination of moonlight and high tide coincide in order to aid, respectively, the airborne and beach landings, Allied commanders chose June 5. However, because of unfavorable weather conditions Eisenhower was forced to delay for 24 hours. The next window of opportunity would not be until late July, Eisenhower made the decision to proceed with the invasion. 

D-Day was the name for the invasion of Normandy, the invasion was originally planned to take place on June 5 but due to several other failed launch dates due to bad weather, it took place on June 6, 1944, under the leadership of Supreme Allied Commander General Dwight D. Eisenhower. Eisenhower was assisted by three British commanders who were in charge, respectively, of air, sea, and land forces: Air Chief Marshal Sir Trafford Leigh-Mallory, Admiral Sir Bertram H. Ramsay, and Field Marshal Montgomery. Likewise, Air Chief Marshal Sir Arthur Tedder, the deputy supreme Allied commander, and General Walter Bedell Smith, Eisenhower's chief of staff, supervised the massive logistical task of coordinating the men and materials needed for the invasion.

Montgomery as the head of land operations pushed for five beachheads, which Eisenhower named "Utah" and "Omaha," whereupon he them to the American-led Western Task Force, and beaches "Gold," "Juno," and "Sword," assigned to the British-led Eastern Task Force. Both task forces comprised the 21st Army Group, consisting of the British Second Army, commanded by Lieutenant General Sir Miles Dempsey; the Canadian First Army, commanded by General Henry D. G. Crerar; and the U.S. First Army, commanded by Lieutenant General Omar N. Bradley. **

 The Calais Deception
 Despite the Allies' choice of Normandy, they had decided that Calais would play a part an integral part in their plan. Many in the German High Command, most notably Hitler himself, believed Calais to be the actual target of any Allied offensive against the mainland. Through a deception operation known as Operation Fortitude, the Allies broadcast fake radio traffic and invented nonexistent armies that pointed toward an invasion at Calais. Hitler and the High Command, headed by Field Marshal Wilhelm Keitel, believed that any actions by the Allies against the mainland would simply be a diversionary tactic to draw away from the real target of Calais. Consequently, the Germans concentrated a majority of their best reserves, including the powerful 15th Army (Armee Oberkommando), in the Pas de Calais region, with the weaker 7th Army stationed at Normandy—a maneuver that would prove costly when D-day arrived.

To keep the ruse going the Allied command had notable and renowned generals like George Patton execute fake inspections of the troops there and even had them practice fake landing assaults.