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 .
