6 June 1944. More than 150,000 men cross the Channel by sea and air and have to be right on the first try. At Omaha the Americans are pinned on the sand for hours; Utah goes almost too easily. British and Canadian troops at Gold, Juno and Sword get further inland than anyone, and still short of Caen. The paratroopers are scattered across the fields.
Why then
The Allies have command of the air, the shipping, and a deception that keeps German reserves waiting for a landing at Calais. Stalin has demanded a second front since 1941. A break in the weather sets the date.
What they wanted
Eisenhower needs a beachhead that cannot be pushed back into the sea. Rommel believes the invasion must be beaten on the beach. Churchill hopes to take France back without another Somme, and gets the hedgerows instead.
What changed
Normandy takes two months of fighting through hedgerows. Sixteen days after the landings, the Red Army's summer offensive, Operation Bagration, destroys a whole German army group in Belarus. Paris is free in August. Germany now faces armies in the west, the east and Italy at once.
Still argued
Some historians argue the Allies' material weight made success near certain once they were ashore; others point to Omaha that morning, where the landing nearly did not hold.