World War II may have been won by millions of brave men who risked and gave their lives to fight the ultimate tyranny in the world. However, the outcome could have been a whole lot different if it weren't for one very convincing spy.

Juan Pujol Garcia of Lisbon, Portugal served the British army has an undercover operative in the ranks of the Axis powers. He was so good at acting as a double agent that the British gave him the moniker "Agent Garbo." His amazing life story has been chronicled in a new book called "Agent Garbo: The Brilliant Eccentric Secret Agent Who Tricked Hitler & Saved D-Day."

Garcia's war story starts in his early 30s as a failed businessman and husband. Despite his unsuccessful attempts at carving a normal life for himself, he was very adept at playing "the double-cross game" and decided to offer his services to the British army in the fight against the Third Reich.

He had no money to fly to London, so he worked his way into the German military and started feeding information to them that was totally false. Not only did the Germans believe the information, but the British believed it as well when they heard the news that a defector might be in the Germans' ranks. Pretty soon, they conspired with Garcia to feed him fake movements and work undercover for them to dismantle the German military.

The biggest blow came just before the historic Normandy invasion. Garcia actually convinced Hitler himself not to supply the area with troops by insisting the reports of the invasion was completely fake in a long and detailed telegram. Hitler retreated his troops to the wrong area supplied by Garcia's information and the rest, as they say, is history.