Winston Churchill, Franklin Delano Roosevelt, and Joseph Stalin were considered the Big Three of the Allied Forces in WWII. If any of them were captured or assassinated, it would have spelled the end for the Allied Forces and history would have been much different than it is today.
However, when the planned assassination mission called Long Jump, which was led by Otto Skorzeny, had been put into motion, the Axis didn't realize that the Soviets had learned about their plan through one of their guerrillas who infiltrated their ranks.
When Hitler was putting together a team to attempt the assassination of the Big Three, Skorzeny was the man he turned to as the leader. The plan they developed was called Long Jump.
Meanwhile, the Soviets had a group of guerrillas operating in the Ukraine which was occupied by the Germans. One of the guerrillas was Nikolai Kuznetsov, the famed Soviet espionage officer, who spoke perfect German and was masquerading as a German lieutenant.
He became friends with SS-Sturmbannführer Ulrich von Ortel, who gave details of the Long Jump plan one night while they were drinking together. Ortel even offfered to introduce Kuznetsov to Skorzeny.
The Soviets were now aware of the German plans but allowed them to continue to proceed without intervening.
Learn more about the details of the event and the outcome at War History Online.
(Image credit: Bundesarchiv, Bild 183-R81453 / CC-BY-SA 3.0; Wikimedia Commons)