On June 6, 1944, an armada of 150,000 Allied soldiers landed on five beaches in Normandy, France. Their mission: to free Europe from the tyranny of Nazi domination. This event was the largest seaborne invasion in history, and included a collection of American, British, Canadian and Australian troops, with soldiers coming from a total of 12 countries.

Launched as the "Operation Overlord" campaign, the battle that initiated the invasion of Normandy is forever etched in history by one word: D-Day. It would be the day on which the rest of World War II turned.

Some historians consider it the single most important day in the 20th century. The attack had been planned for more than a year. The amphibious landings were supported by an airborne drop of 13,000 men later that night. More than 11,000 aircraft and 5,000 ships landed across the five Normandy beachheads, code-named Utah, Gold, Juno, Sword, and Omaha. The day was plagued by bad weather. Through it all, the attack remained a secret, one that surprised the Germans.

U.S. troops wade ashore during the Allied invasion of Normandy, France, June 6, 1944. D-Day was one of the world's most gut-wrenching and consequential battles. Nearly 160,000 American, British, Canadian and French troops participated in the invasion of northwest France, known as Operation Overlord. More than 9,000 Allied forces were killed or wounded. AP Photo

Upon landing, Allied soldiers encountered thousands of German soldiers dug into high-ground barracks with powerful 150 mm machine guns ready to clip them as they emerged off metal landing crafts. Hundreds of men died instantly; some drowned from the weight of their supply packs. Even if they survived Nazi gunfire, Allied troops encountered heavily fortified obstacles like wooden stakes, barbed wire and metal tripods.

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The Allies would not be deterred. Between 4,000 and 9,000 Nazi troops were killed. By the end of the evening, the Germans were in retreat and the Allies had established control of the area.

The cost of victory was tremendous. There were an estimated 10,000 Allied casualties, with 4,414 confirmed dead. But out of this carnage emerged a new way forward, as the western front was finally opened against Hitler, marking the beginning of his downfall.

This invasion of Normandy resulted in a decisive Allied victory over Axis powers in France, and set the stage for an Allied victory over all of Europe one year later.