 The fate of the world depended on its success. But how did two million people keep D-Day a secret? On June 6, 1944, 156,000 soldiers traveled through the English Channel to arrive on a 50-mile stretch of beach in Normandy. It was known as Operation Overlord, and it's arguably the single greatest example of teamwork ever carried out. It took three years to orchestrate and relied on the cooperation of 12 nations, over 2 million military personnel, and double agents from across the globe, all operating in complete secrecy. With so many moving pieces, they needed a code word, which many believe is the British invasion of German-occupied territory. Not even King George VI knew the details. The logistics of such a massive operation included a staggering amount of coordinated efforts. By June 11, we had 326,000 troops in Normandy. The big question, how do they move all these supplies without the enemy catching on? Enter the Double Cross System, aka the 20 Committee, a massive counter-espionage operation designed to spread misinformation. One of the greatest efforts was a top-secret plan intended to make the Germans think an attack would take place here, Pas de Calais, the closest point between Britain and France, miles away from Omaha Beach, so they set up divisions right across the channel at the coast of Dover. Unfortunately for the Nazis, it was, as they say, all smoke and mirrors. A fake out. A shell fleet made up of fake divisions, inflatable trucks, rubber paratroopers, and decoy landing craft. This fake division was further reinforced by cunning double agents like Spanish-born Garbo, who convinced Hitler that a million-man army would appear at Calais, which kept several of Germany's best Panzer divisions back, even while Normandy was being attacked. So convincing was Garbo that during the war, the Nazis never found out he was working against them, even awarding him the Distinguished Iron Cross. He is one of the few in history who has won military distinctions from both sides of the war. Hitler was convinced to hold off on sending reinforcements to Normandy, making it one of the most successful military operations ever designed. And it took the teamwork of nations to make it happen. D-Day was the tipping point of the war. It literally changed the course of the world as we know it. It brought together men and women from all walks of life, from different countries with different backgrounds, beliefs, all unified under the singular vision of freedom. The extensive, precise planning took trust, bravery, and coordination on the grandest of scales, and will go down in history as one of the greatest team efforts ever devised.