By May 1944, more than 4,000 warships and 1,200 planes — the largest armada in history — prepared to invade Nazi-occupied France.

For most of the 176,000 soldiers, sailors and airmen who were to take part in D-Day, confirmation came on the eve of the invasion, when they received copies of Supreme Allied Commander Gen. Dwight D. Eisenhower's "Order of the Day."

Some sailors heard from Eisenhower via an on-ship radio broadcast.

"Soldiers, sailors and airmen of the Allied expeditionary force," Eisenhower began. "You are about to embark upon the great crusade, toward which we have striven these many months. The eyes of the world are upon you."

Nobody could predict the outcome, and Eisenhower even prepared a message to the world in case of failure and retreat. But to the troops — many of whom had only hours to live — Eisenhower breached no possibility of defeat, telling them: "We will accept nothing less than full victory."