On this day in history, the D-Day operation of June 6, 1944, brought together the land, air and sea forces of the Allied armies in what became known as the largest amphibious invasion in military history, according to the Dwight D. Eisenhower Presidential Library, Museum and Boyhood Home in Abilene, Kansas.

"The operation, given the codename OVERLORD, delivered five naval assault divisions to the beaches of Normandy, France," notes the same source.

"The beaches were given the code names: UTAH, OMAHA, GOLD, JUNO and SWORD."

The historic invasion force that landed on D-Day included 7,000 ships and landing craft manned by over 195,000 naval personnel from eight Allied countries and almost 133,000 troops from the United States, the British Commonwealth and Allies.

The buildup to D-Day was highly coordinated.

In May 1944, the Western Allies were finally prepared to deliver their greatest blow of World War II, a cross-channel invasion of northern France, the National WWII Museum indicates, codenamed OVERLORD.

General Dwight D. Eisenhower was supreme commander of the operation that ultimately involved the coordinated efforts of 12 nations, notes the same source.

Following deliberation, it was decided that the landings would take place on the long, sloping beaches of Normandy — and it was there that the Allies would have the element of surprise, the same source cites.

"The German high command expected the attack to come in the Pas de Calais region, north of the river Seine where the English Channel is narrowest," says the National WWII Museum.

"It was here that Hitler had put the bulk of his panzer divisions after being tipped off by Allied undercover agents posing as German sympathizers that the invasion would take place in the Pas de Calais."

The invasion was conducted in two main phases: an airborne assault and amphibious landings, says the Imperial War Museum in the U.K.

Shortly after midnight on June 6, over 18,000 Allied paratroopers were dropped into the invasion area to provide tactical support for infantry divisions on the beaches, notes the same source.

Also, Allied air forces flew over 14,000 sorties in support of the landings and, having secured air supremacy prior to the invasion, recounts the Imperial War Museum in the U.K.

There were challenges of mounting a successful landing, as surprise was an essential element of the Allied invasion plan, according to the National WWII Museum.

"It was especially daunting as the English Channel was notorious for its rough seas and unpredictable weather, and the enemy had spent months constructing the Atlantic Wall, a 2,400-mile line of obstacles," says the same source.

By daybreak on June 6, 1944, thousands of paratroopers and glider troops were already on the ground behind enemy lines, securing bridges and exit roads, says History.com.

The amphibious invasions began at 6:30 a.m., says multiple sources.

The British and Canadians overcame some opposition to capture beaches codenamed Gold, Juno and Sword, as did the Americans at Utah Beach, according to History.com.

The Germans were aware of the importance of the sector designated Omaha Beach, which the Allies would need to connect and secure the beachheads together, and made certain it was heavily defended, says the National D-Day Memorial Foundation.

"Fortifications and elevated terrain meant the American landing on Omaha would be the bloodiest that day," says the same source.

U.S. forces faced heavy resistance at Omaha Beach, where there were over 2,000 American casualties, says History.com.

"However, by day’s end, approximately 156,000 Allied troops had successfully stormed Normandy’s beaches," says the same source.

More than 4,000 Allied troops lost their lives in the D-Day invasion, with thousands more wounded or missing, according to some estimates, says History.com.

The British secured Gold Beach with the help of artillery, tanks and air support, says the National D-Day Memorial Foundation.

Canadian forces pushed the Germans out and secured Juno’s beachhead by mid-afternoon, says the same source.

"Tasked with securing Sword Beach, the British were three miles from their intended objective at Caen by day’s end," says the same source.

"Nightfall on D-Day found Allied forces past the German defenses on all five beachheads. Hitler’s vaunted Atlantic Wall lasted less than 24 hours."

Less than a week later, on June 11, the beaches were fully secured and over 326,000 troops, more than 50,000 vehicles and some 100,000 tons of equipment had landed at Normandy, History.com says.

On June 26, 1944, the Allies captured the French port of Cherbourg and the Germans were on the retreat, says NPR.

By June 30, over 850,000 men, 148,000 vehicles, and 570,000 tons of supplies had landed on the Normandy shores, notes the Dwight D. Eisenhower Presidential Library.

"Fighting by the brave soldiers, sailors, and airmen of the allied forces western front, and Russian forces on the eastern front, led to the defeat of German Nazi forces," the same source says.

On Aug. 25, 1944, Allied troops, with the help of the French resistance led by Gen. Charles de Gaulle, liberated Paris after four years of German occupation, says NPR.

The following spring, on May 7, 1945, Gen. Dwight Eisenhower accepted Germany's unconditional surrender at Reims, France.

By midnight on May 8, 1945, the war in Europe was officially over.