When on D-Day-June 6, 1944-Allied armies landed in Normandy on the northwestern coast of France, possibly the one most critical event of World War II unfolded; for upon the outcome of the invasion hung the fate of Europe. If the invasion failed, the United States might turn its full attention to the enemy in the Pacific-Japan-leaving Britain alone, with most of its resources spent in mounting the invasion. That would enable Nazi Germany to muster all its strength against the Soviet Union. By the time American forces returned to Europe-if indeed, they ever returned-Germany might be master of the entire continent.
Although fewer Allied ground troops went ashore on D-Day than on the first day of the earlier invasion of Sicily, the invasion of Normandy was in total history's greatest amphibious operation, involving on the first day 5,000 ships, the largest armada ever assembled; 11,000 aircraft (following months of preliminary bombardment); and approximately 154,000 British, Canadian and American soldiers, including 23,000 arriving by parachute and glider. The invasion also involved a long-range deception plan on a scale the world had never before seen and the clandestine operations of tens of thousands of Allied resistance fighters in Nazi-occupied countries of western Europe.
American General Dwight D. Eisenhower was named supreme commander for the allies in Europe. British General, Sir Frederick Morgan, established a combined American-British headquarters known as COSSAC, for Chief of Staff to the Supreme Allied Commander. COSSAC developed a number of plans for the Allies, most notable was that of Operation Overlord, a full scale invasion of France across the English Channel.
Eisenhower felt that COSSAC's plan was a sound operation. After reviewing the disastrous hit-and-run raid in 1942 in Dieppe, planners decided that the strength of German defenses required not a number of separate assaults by relatively small units but an immense concentration of power in a single main landing. The invasion site would have to be close to at least one major port and airbase to allow for efficient supply lines. Possible sites included among others, the Pas de Calais across the Strait of Dover, and the beaches of Cotentin. It was decided by the Allies that the beaches of Cotentin would be the landing site for Operation Overlord.
In my opinion, the primary reason that the invasion worked was deception. Deception to mislead the Germans as to the time and place of the invasion. To accomplish this, the British already had a plan known as Jael, which involved whispering campaigns in diplomatic posts around the world and various distractions to keep German eyes focused anywhere but on the coast of northwestern France. An important point to the deception was Ultra, code name for intelligence obtained from intercepts of German radio traffic. This was made possible by the British early in the war having broken the code of the standard German radio enciphering machine, the Enigma. Through Ultra the Allied high command knew what the Germans expected the Allies to do and thus could plant information either to reinforce an existing false view or to feed information through German agents, most of it false but enough of it true-and thus sometimes involving sacrifice of Allied troops, agents or resistance forces in occupied countries-to maintain the credibility of the German agents.
Six days before the targeted date of June 5, troops boarded ships, transports, aircraft all along the southern and southwestern coasts of England. All was ready for one of history's most dramatic and momentous events. One important question was left unanswered though: what did the Germans know?
Under Operation Fortitude, a fictitious American force-the 1st Army Group-assembled just across the Channel from the Pas de Calais. Dummy troops, false radio traffic, dummy landing craft in the bay of the Thames river, huge but unoccupied camps, dummy tanks-all contributed to the deception.
Although the Allied commanders could not know it until their troops were ashore, their deception had been remarkably successful. As time for the invasion neared, the German's focus of the deception had shifted from the regions of the Balkans and Norway to the Pas de Calais. The concentration of Allied troops was so great, that an invasion of France seemed inevitable. Bombing attacks, sabotage by the French Resistance and false messages from compromised German agents all focused on the Pas de Calais with only minimal attention to Normandy. Also, German intelligence thought that the Allies had 90 divisions ready for the invasion (really only 39), so that even after the invasion of Normandy, the belief could still exist that Normandy was just a preliminary measure and the main invasion of the Pas de Calais was still to come. None of the German high command in France doubted that the invasion would strike the Pas de Calais. The Fü hrer himself, Adolf Hitler, had an intuition that the invasion would come to Normandy but was unable to incite his commanders to make more than minimal reinforcement there.
Due to weather complications, the first step in the invasion began a day late, on June 6 around 12:15 am. An air attack on Normandy. The Germans saw the airborne assault as nothing more than a raid or at most a diversionary attack.
As the airborne landings continued, Field Marshal von Rundstedt nevertheless decided that even if the assault was a diversionary attack, it had to be defeated. Around 4:00 am, he ordered two panzer divisions to prepare for counter attack, but when he reported what he had done to the high command in Germany, word came back to halt the divisions pending approval from Hitler. That would be a long time coming, for Hitler's staff was reluctant to disturb the Fü hrer's sleep.
For the following 12 hours, Allied forces landed on five beaches defeating with minimal casualties, the German defenses.
It was 4 pm on D-Day before Hitler at last approved the deployment of the two panzer divisions. Allied deception had been remarkably effective and because Hitler had been sleeping and was then slow to carry out any action, German power which could have spelled defeat for the invasion had been withheld. The rest of the armoured reserve in France-five divisions-and the 19 divisions of the massive Fifteenth Army in the Pas de Calais, stood idle feeling that the main invasion was still to come.
The next day, after word reached Hitler that German troops had found copies of U.S. operation orders indicating that the landing in Normandy constituted the main invasion, he ordered the panzer reserve into action, but Allied intelligence was ready for such an emergency. Through Ultra the Allied command learned of Hitler's orders, and through a compromised German agent known as Brutus, it sent a word that the American corps orders were a plant. The main invasion, Brutus reported, was still to come in the Pas de Calais. Hitler canceled his orders.
Had Allied commanders known of the near-bankruptcy of troops on the German side, they would have had more cause for encouragement. The Seventh Army (German defense of Normandy) had thrown into the battle every major unit available. The commander of the Seventh Army was reluctant to commit any forces from the West (Brittany) to the invasion, fearful of a second Allied landing. Meanwhile, most German officials-their eyes blurred by Allied deception-continued to believe that a bigger landing was still to come in the Pas de Calais.
In my opinion, the primary reason that the invasion worked was deception. D-Day was a tremendous achievement for British, Canadian and American fighting men, but it also owed an immeasurable debt to Ultra and to the deception that Ultra made possible.