During World War II, an impulsive, artistic young woman named Lily Sergueiew fled occupied France to live near friends in England. From there she began sending regular radio transmissions to the Nazis. In May 1944, Sergueiew informed her German spymaster that she was romantically involved with an American officer. Through him, she claimed to have learned all sorts of specifics about the First U.S. Army Group, a large force massing in southeast England for a summer attack on the Pas de Calais in France.

On June 6, D-Day, the Allies landed in France - not on the Pas de Calais but in Normandy. However, based on the information provided by Sergueiew and a thick network of other spies, Hitler was convinced that Normandy was a mere diversion. Believing that the real assault was still to come, he ordered General Rommel not to move his formidable Fifteenth Army from the Pas de Calais.

The rest, as they say, is history. The second assault never came, because the First U.S. Army Group was largely a "notional" - imaginary - force. The landing craft that filled England's southeast ports and the 3-mile-square oil dock at Dover - clear signs of military buildup - were actually giant stage sets made of scrap materials. The ruse worked. Rommel's immobility gave the Allies their chance to press on to Paris, Berlin, and eventual victory.

What was the real role of Lily Sergueiew? Or of Juan Garcia Pujol, the silver-tongued Spanish spy who had forewarned the Germans of D-Day and sworn to them that it was only a rehearsal? Or of the other spies scattered around Britain? Clearly, they were all double agents. But how did they gain the trust of the Nazis when their reports were scripted by British intelligence? How did the Allies pull off such an elaborate deception?

That's the story Shelburne resident Hervie Haufler tells in his second book, The Spies Who Never Were, published last January by Penguin. In this compact, meat-and-potatoes history, WWII veteran Haufler explains how British intelligence functioned like a well-oiled machine to "turn" suspected German agents and recruit others to the cause, and then to maintain their credibility with the German Abwehr intelligence service. Not one of the spies who reported to the Abwehr from England was what he or she appeared to be, and 120 people played this role at some point during the war.

Haufler gives a chapter to each of the major double agents, who came from a dazzling array of backgrounds and had "code names such as Balloon, Careless, Gelatine, Hamlet, Lipstick, Snark, Mullet, Puppet and Treasure." Wulf Schmidt, a German nabbed after he parachuted into Britain, underwent a "conversion" and decided to serve his captors. Eddie Chapman, a career criminal, embraced spying as his route to fame and fortune. Shy Juan Pujol had to use his novelistic imagination just to get the notice of the British, who initially rejected his offers of service. He contacted the Germans and began sending them bulletins supposedly from England and full of persuasive misinformation, "even though he had never been there." With British complicity, he later concocted a network of 27 subagents who didn't exist.

Then there was Dusko Popov, whose story came closest to a James Bond movie - at least as he later told it. The wealthy Yugoslav playboy claimed after the war that he had tried in vain to warn J. Edgar Hoover about the imminent attack on Pearl Harbor.

Unlike Hoover's FBI, which Haufler describes as "[seeking] every possible opportunity to prompt headlines" with the dramatic capture of spies, British intelligence worked in intense secrecy. That secrecy extended into the postwar period, and it affected Haufler himself.

"In 1942," Haufler says in an email, "I enlisted in the only service that would overlook my poor eyesight: the U.S. Army Signal Corps." He was part of a group of G.I.s who were trained for a role in the British codebreaking program known as Ultra Secret, without which the double agent system could not have succeeded. He was assigned to a station in Kent where radio operators intercepted coded German messages. As a cryptographer, Haufler's job was to guide the operators to the frequency where they would find a particular German network on a given day. (The Germans regularly switched frequencies according to a set of formulas, which the British had decoded.) The messages were then sent on to Bletchley Park, near London, where British mathematicians had devised a way to crack the Nazis' Enigma coding machine.

Haufler discovered this only much later, when the efforts of the cryptanalysts were publicized in books and movies like Enigma. "We knew the central place only as Station X," he says in a phone interview. "Military intelligence is ruled by the need to know. You learn only what you need to know to do your job. I wasn't an officer, I was an enlisted man, so my need to know was not very big."

After the war ended, Haufler and about 10,000 other participants in the codebreaking system were sworn to secrecy about the work they had done. The British "were wary about the Russians in the Cold War," Haufler points out, and didn't want to expose one of their greatest weapons. He adds, "Our outfits were so dedicated to this vow that we lost track of each other."

It took 30 years for the veil to fall. A British officer was finally permitted to write a book detailing the triumph of the codebreakers, and accounts of the double agents - also officially classified - began to surface. "When I found out the full story I became obsessed with that secret war of military intelligence," Haufler says.

After the war, business concerns gave Haufler little time for writing until he and his wife closed their consulting company and retired to New Hampshire. Haufler spent six years on his first book, Codebreakers' Victory, which he researched extensively in England; it was published in 2003.

Next, Haufler's agent floated his idea for The Spies Who Never Were to Penguin, where Haufler says that "my editor there saw special promise in it - so much so that he wanted the manuscript in six months. I gulped and signed the contract." Haufler didn't have time to go to the U.K. himself, so he hired a professional researcher who turned out to be "a marvel. He would find documents I should see, digitally photograph them and burn them onto a compact disc," Haufler says. "He would then send me some 1200 pages on a single CD."

Haufler's account of British espionage in WWII suggests that Machiavelli was right - sometimes the fox is mightier than the lion, or cunningly gathered intelligence does what sheer force cannot. What does he think of the questions that have been raised about U.S. intelligence since the attacks of 9/11?

In WWII, Haufler says, "There's a very important lesson that we are not likely to learn. That is, not to scatter our intelligence operations into many pieces. The British in WWII did it right. They broke down the barriers to interservice rivalries. Control of the double agents was given to the one operation, especially formed for that person. Each service had a representative on the committee that controlled the double agents. When the U.S. was in control of war in Pacific, they never did use miliary intelligence too well, because it was split up among the services, each one guarding its turf."

Haufler and his wife recently moved to Vermont to live at Wake Robin Continuing Care Retirement Community. "I know I'm a lucky old scribbler, to have my first two books published when I'm in my eighties," says the author, now 87. "But I plan to keep on scribbling as long as my energy and wits hold out."

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Another octagenarian "scribbler," Vermont State Poet Grace Paley, will read at St. Johnsbury Academy this Friday. Local novelist and memoirist Reeve Lindbergh will introduce her. Come see why Salon.com called Paley a "sagacious elf."

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Two Vermont writers got some good news last month. Dorothy Gannon of Norwich and Paige Ackerson-Kiely of Lincoln were announced as the winners of Poets & Writers magazine's annual Writers' Exchange Contest for fiction and poetry, respectively. Since 1984, the magazine's judges have chosen promising writers from a selected state for a trip to New York to meet with agents and editors. Well-known novelists Mona Simpson and Sue Monk Kidd are among the previous winners, but this is the first time Vermonters have had a chance to compete for a leg up in the lit world.