They were young men, mostly teenagers, who came from the United States, Britain and Canada. Only one in seven had ever before seen combat.

More than 130,000 troops crossed the English Channel and landed on the beaches on D-Day. They were supported by over 5,000 ships and 11,000 airplanes. It was the largest air, land and sea operation the world had ever seen. It has never been equaled since.

Planning was intense, success by no means assured. The Allied forces faced Hitler's extensive Atlantic Wall, fortified with tank-top turrets, barbed wire and a million mines.

When it was over, the Wall had been breached. The Allies had gained a foothold in Europe, and the Nazis were in retreat. June 6, 1944, was the turning point, day one of the drive to ultimate Allied victory.

But the cost was high. The Allied Forces suffered nearly 10,000 casualties, including more than 4,000 dead. On notorious Omaha Beach, Yanks were slaughtered wholesale.

About 71,000 Americans took part in the D-Day invasion. No one knows how many survive today, but their number is surely dwindling. Most are in their mid-80s, and fading away fast. An estimated 1,100 World War II vets die each day. In 2014, when the 70th anniversary of D-Day is marked, few D-Day veterans are likely to be alive.

Contact staff writer Art Carey at 610-701-7623 or acarey@phillynews.com.