The Allied commander, U.S. General Dwight D. Eisenhower, gives instructions to paratroopers at the beginning of D-Day landing operations, in England, June 1944.

Prior to the invasion, Gen. Eisenhower broadcast a message to the soldiers, sailors and airmen of the Allied Expeditionary Force! which said, in part: "You are about to embark upon a great crusade, toward which we have striven these many months. The eyes of the world are upon you. The hopes and prayers of liberty-loving people everywhere march with you. In company with our brave Allies and brothers in arms on other fronts, you will bring about the destruction of the German war machine, the elimination of Nazi tyranny over the oppressed peoples of Europe, and security for ourselves in a free world."

Operation Overlord -- the code-name for the invasion of Normandy -- involved an aerial and amphibious assault along a 50-mile stretch of heavily-fortified coastline of Nazi-occupied France, involving about 7,000 vessels, 12,000 aircraft and nearly 160,000 Allied troops.

On June 4, 1944, medium bombers of the Ninth Air Force (left) began two days of bombardment of the coast near Pointe du Hoc, France -- "Omaha Beach" -- prior to the amphibious assault.

Jeeps and trucks are loaded onto landing craft (LCTs) in an English port prior to the launch of the D-Day invasion.

On the evening before the beach assault, 23,000 British and American paratroopers landed in France, behind the defensive lines of the German Army.

American troops board landing craft in Britain in preparation of the invasion of France on D-Day.

American assault troops huddle behind the shield in a landing craft approaching Utah Beach, June 6, 1944.

A frame from color footage shows the battleship USS Texas firing salvos at Axis positions during the Allied landing at Omaha Beach, on D-Day, June 6, 1944.

American troops disembark from landing crafts at Omaha Beach during D-Day, June 6, 1944.

The USS Nevada fires its 14" forward guns at German position on shore at Utah Beach, during the D-Day Invasion, June 6, 1944.

American troops of the 4th Infantry Division (the "Famous Fourth") land on Utah Beach June 6, 1944, during the D-Day Invasion.

An aerial view taken from a B-26 shows 32 American merchant ships which were purposefully sunk off the coast of Normandy to support Allied forces. With Army gunners onboard, the ships served as both a breakwater and as offshore anti-aircraft gun platforms to protect Allied forces storming the beaches on D-Day, June 6, 1944.

Survivors of a sunken landing craft are helped from their life raft onto Omaha Beach, June 4, 1944.

A "Rhino" ferry -- 42-by-176 foot flat-bottomed pontoon barges, used to transport supplies and vehicles from ship to shore -- is assisted by a tug as it approaches the beach at Normandy on D-Day.

Canadian soldiers from the 9th Brigade land with their bicycles at Juno Beach in Bernieres-sur-Mer during D-Day, June 6, 1944.

Two survivors of a ship hit by enemy fire and sunk are rescued by a U.S. Coast Guard boat off Normandy, June 6, 1944.

Crossed rifles lay in the sand as a tribute to a fallen American soldier, on the shores of Normandy, June 6, 1944.

French commandos equipped with bikes disembark from landing crafts during the D-Day Invasion, June 6, 1944.

American troops are ready to disembark from crafts during D-Day, June 6, 1944 after Allied forces stormed the Normandy beaches.

Canadian soldiers land on Courseulles beach in Normandy, June 6, 1944 as Allied forces storm Normandy on D-Day, June 6, 1944.

American troops land on the beaches of Normandy during the historic D-Day Invasion, June 6, 1944.

Soldiers of the 8th Infantry Regiment, 4th Infantry Division, strike out over the seawall at Utah Beach, June 6, 1944.

A view of landing craft, barrage balloons, and Allied troops landing at Normandy, France on D-Day, June 6, 1944.

U.S. soldiers gather around trucks disembarking from crafts shortly after the D-Day landing, June 6, 1944.

Allied soldiers on the beaches of Normandy after the D-Day invasion, June 6, 1944.

A view of wounded servicemen of the 3rd Battalion, 16th Infantry Regiment, 1st Infantry Division, after storming Omaha Beach on D-Day, June 6, 1944.

Soldiers of the Allied Expeditionary Corps stand sentry on a beach of Normandy in Northern France during June 1944 operations, after the historic D-Day Invasion.

An American soldier has just landed his glider after Allied forces stormed the Normandy beaches, on D-Day, June 6, 1944.

Crowds read the news ticker for the latest on the D-Day Invasion, in Times Square, New York City, June 6, 1944.

U.S. soldiers surround a burning German tank in a village in France in June 1944, after Allied forces stormed the Normandy beaches during D-Day.

British soldiers cross the village of Douet, France, June 8, 1944, after the town of Bayeux fell during the Allied invasion of D-Day.

Allied soldiers meet a herd of cows as they make their way through the Normandy countryside, a few days after Allied troops landed on the beaches of northwest France.

Visitors look at the crosses in the American Military Cemetery June 5, 2003 near Omaha Beach, Colleville sur Mer in Normandy, France. At Omaha Beach alone, more than 3,000 American personnel were killed, wounded or missing by the end of the first day of action on June 6, 1944.

For more info:
National WWII Museum, New Orleans
National D-Day Memorial, Bedford, Va.
Normandy American Cemetery and Memorial
General Eisenhower's D-Day Message (with audio)

By CBSNews.com senior producer David Morgan