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.