Americans awoke 70 years ago this morning to learn that Allied troops had stormed ashore on the Normandy coast of France. Some troops already were making their way inland after encountering surprisingly light resistance; others, especially Americans at the "Omaha" beachhead, were pinned down by a fierce German defense.

The scope of the operation was immense and historic - nearly 7,000 ships, more than 195,000 sailors and more than 156,000 soldiers, including 73,000 Americans, had crossed the English Channel. Operation Overlord began the liberation of Western Europe and sealed the demise of Nazi Germany, which already had sustained massive losses in the east and from incessant British and American bombing campaigns.

Today, 70 years out, only a handful of that brave legion remain to observe the anniversary.

Unfortunately, their incredible exploits are in danger of fading into the mist of history. A survey by the American Council of Trustees and Alumni, released this week, found that 25 percent of American adults don't know that "D-Day" occurred during World War II. Only 54 percent knew that Gen. Dwight Eisenhower was the supreme commander of Allied forces, and 28 percent could not identify him.

Today's total U.S. population is about 317 million, a quarter of which is more than 79 million. Subtract the kids and, by percentage, the number of adults who can't place D-Day in World War II probably is somewhere near the total U.S. population in 1944, about 134 million.

America's genius always has been its ability to incessantly look forward rather than back. But the nation inevitably will find it more difficult to move forward if we don't understand - and appreciate - the commitment, courage and sacrifice that mark where we have been.