One of East Germany's top spies was actually an American soldier. Jeff Carney defected to the Communist state in 1983 and fed the notorious Stasi with reams of valuable information. He has now written a book about his experiences.

Berlin's Marienfelde district in the fall of 1983: The day Jeff Carney helped save the world was just four hours old. Carney, a 20-year-old surveillance specialist with the United States Air Force, was sitting in the early morning in front of the equipment he used to eavesdrop on the East. He was on the night shift, and there was nothing special to report.

Then his supervisor told him about a secret operation that was set to take place just a few hours later. It was a war game of sorts, and it involved US fighter jets that would come within threatening range of Soviet airspace, triggering alarm signals on the Russians' radar screen and a general state of confusion. The planners expected that the other side would become so unnerved over the maneuver that emergency response procedures would be set in motion, revealing them to US reconnaissance.

But what if the Russians thought it was an actual attack and launched a counter-attack? Carney, who had been working as an agent for the East German Ministry for State Security, known as the Stasi, for a few months, had mere hours to act. First, he had to finish his shift, but then he hurried to see his Stasi contact, a teacher in West Berlin. His message made it in time; the Soviets were alerted that it was a fake maneuver, but not an actual attack....