Revealed: how a Nazi document shredder became America's most valuable spy

To outsiders Fritz Kolbe was a typically correct Nazi official. The balding, impish German, who liked wearing lederhosen, worked as a mere bureaucrat in Adolf Hitler's Foreign Ministry for most of the Second World War, where he was employed shredding documents.

To outsiders Fritz Kolbe was a typically correct Nazi official. The balding, impish German, who liked wearing lederhosen, worked as a mere bureaucrat in Adolf Hitler's Foreign Ministry for most of the Second World War, where he was employed shredding documents.

Yet for what was later to become the CIA, Fritz Kolbe was and still is "the most important spy of the Second World War". Kolbe loathed the Nazi regime and was prepared to do everything in his power to bring about its downfall.

He smuggled hundreds of top-secret files to American intelligence from 1943 onwards, continuing undetected until the end of the war. Rejected by postwar Germany, he was reduced to becoming a salesman for an American chainsaw manufacturer.

The information that Kolbe supplied to Allen Dulles, who later founded the CIA, included secrets about where the Germans expected the Allies to land in Normandy, key facts about the Nazi V1 and V2 rockets and Japanese military plans in South-east Asia. Kolbe even exposed a butler working in the British embassy in Istanbul as a German spy.

Richard Helms, a former CIA boss, described Kolbe's information as "the most important ever supplied by an agent working for the Allies during the whole of World War Two".

Spurned by the British who assumed he was a "Nazi plant" because he refused to accept payment for information, Kolbe supplied his secrets exclusively to the American OSS. Kolbe's story is little known in Britain, and in Germany - where he was once dismissed as a traitor - and he has never been honoured for his wartime role.

A new book by a French historian, published in Germany this week, attempts to correct the imbalance. Fritz Kolbe, by Lucas Delattre, has been timed to appear as Germany prepares to mark the 60th anniversary of the failed 20 July 1944 bomb plot against Hitler that was carried out by disaffected members of the Prussian aristocracy in the German army.

The officers who organised the plot will be feted this summer as heroic members of Germany's wartime anti-Nazi resistance. But Kolbe is unlikely to be honoured with them. As Germany's Stern magazine put it this week: "Kolbe's story demonstrates that very ordinary Germans could do something to fight Hitler's madness - and postwar Germany treated him like a leper because of his actions."

Delattre's book, which is the first to draw on the spy's private archives, shows what Kolbe did to undermine the Nazi war machine. For most of the war, Kolbe was employed in the Foreign Ministry and worked directly under Karl Ritter, the chief Nazi liaison officer to the armed forces.

Kolbe saw and photographed the hundreds of top-secret military documents that crossed his desk, even staying in his office during air raids to complete his tasks. Yet his spying career only began in 1943 when he finally succeeded in becoming one of the Third Reich's hand-picked diplomatic couriers, which enabled him to smuggle his information to Switzerland. In August that year he taped two large envelopes containing mimeographed secret documents to his legs and boarded a train to Berne. His official task was to deliver Reich documents to the German embassy in the city, but Kolbe also went to the British where he offered his information for nothing.

MI6, which at the time was under strict orders to mistrust any German purporting to be a spy, dismissed Kolbe as a "Nazi plant" and continued to regard him with suspicion him for most of the war. Unruffled, Kolbe went to the US embassy in Berne, where he was soon introduced to Allen Dulles, the head of regional American intelligence. "I am a German patriot with a conscience and my wish is to shorten this war," Kolbe told the Americans.

Dulles believed Kolbe and agreed to work with him. The information he received over the ensuing war years dramatically boosted his career and helped him to found the CIA. Kolbe smuggled photographed documents, himself and with the aid of other couriers, using watch cases and double-bottomed envelopes to contain the secret information.

Kolbe narrowly escaped arrest after the 20 July plot, but survived the rest of the war unscathed. He worked for American intelligence after 1945 in Germany and Switzerland.

Yet in postwar Germany he was regarded as a traitor. All his applications to join the country's diplomatic corps were rejected although thousands of former Nazis were rehabilitated and employed. Kolbe spent his later life in Europe eking out an existence as a sales rep for an American chainsaw company. He lived for part of the time in a one-room flat before retiring to Switzerland where he died.

Delattre notes that Kolbe's name was not included on a plaque unveiled at the German Foreign Ministry in 1961 which commemorates Germans who resisted the Nazi regime. To this day Germany has not officially honoured his role.