Double Agent: The First Hero of World War II and How the FBI Outwitted and Destroyed a Nazi Spy Ring

Double Agent: The First Hero of World War II and How the FBI Outwitted and Destroyed a Nazi Spy Ring

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by Peter Duffy

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The never-before-told tale of the German-American who infiltrated New York’s Nazi underground in the days leading up to World War II: “Thrilling, well-researched, well-told, fascinating” (Minneapolis Star Tribune).

He was the first hero of World War II and yet the American public has never seen his face. William G. Sebold, a naturalized


The never-before-told tale of the German-American who infiltrated New York’s Nazi underground in the days leading up to World War II: “Thrilling, well-researched, well-told, fascinating” (Minneapolis Star Tribune).

He was the first hero of World War II and yet the American public has never seen his face. William G. Sebold, a naturalized American of German birth, risked his life to become the first double agent in the history of the Federal Bureau of Investigation. He spent sixteen months in the Nazi underground of New York City, consorting with a colorful cast of spies. Sebold was at the center of the most sophisticated investigation yet devised by the FBI, which established a short-wave radio station on Long Island to communicate with Hamburg spymasters and set up a “research office” in Times Square that allowed agents hidden behind a two-way mirror to film meetings conducted between Sebold and the spy suspects.

The result was the arrest and conviction of thirty-three spies, still the largest espionage case in American history. The guilty verdicts were announced in Brooklyn federal court just hours after Adolf Hitler declared war on the United States on December 11, 1941, which meant that the Führer could not call upon a small army of embedded spies and saboteurs during the most trying days of the coming struggle. “As you know,” an FBI official later told J. Edgar Hoover, “Sebold gave us the most outstanding case in Bureau history.”

In Double Agent, Peter Duffy tells this full account. Here is a story “rich with eccentric characters, suspense, and details of spycraft in the war’s early days….The result is a compelling cultural history with all the intricacy and intrigue of a good spy novel” (The Boston Globe).

Editorial Reviews

Library Journal
Veteran journalist Duffy (The Killing of Major Denis Mahon) offers a well-written and well-researched account of espionage between Germany and the United States in the years leading up to the U.S. entry into World War II. William Sebold (1899–1970) was a naturalized American who returned to his native Germany in the mid-1930s and trained to be a spy for the Nazis. When he returned to the United States he turned against his Nazi trainers and became a double agent for the FBI, under the direction of J. Edgar Hoover. Setting up shop in downtown Manhattan, Sebold worked undercover to infiltrate a network of German spies who had no idea they were associating with an FBI agent. In August 1941, the bureau concluded Sebold's sting operation with the arrest and ultimate conviction of 33 German spies. The trial ended on December 11, 1941, the same day Hitler declared war on the United States. This sprightly book covers in detail Sebold's activities as well as those of his German contacts and adds an important chapter to existing histories of espionage during this period. VERDICT A fine contribution to the literature on 20th-century espionage worthy of consideration for most libraries. [See Prepub Alert, 1/10/14.]—Ed Goedeken, Iowa State Univ. Lib., Ames
Publishers Weekly
Journalist Duffy (The Killing of Major Denis Mahon) recounts the first U.S. counterespionage success of WWII: the breaking of a German spy ring centered in New York. It combined “ideologues, opportunists, dupes, adventurers” and a core of agents who initially had a virtual free hand despite F.D.R.’s commitment to sustaining civil liberties. Under Republican pressure, the FBI was made responsible for internal security, and J. Edgar Hoover’s organization demonstrated a high learning curve—thanks in good part to double agent William Sebold. In 1939, Sebold, a German-born naturalized American, was approached by German intelligence, which provided him with elementary training in photography and coding. Returning to the U.S., Sebold contacted the FBI, who in turn offered observation and recording facilities. Sebold proved himself “an actor of consummate skill” in high-risk situations, and when the snare was sprung, 33 spies were arrested, 19 convicted, and the spine of Nazi espionage in the U.S. permanently broken. Hoover was lauded for his handling of the case while Sebold worked in defense plants before sinking back into obscurity. While Duffy’s digressions are distracting and Sebold’s character doesn’t quite hold the narrative together, this remains “one of the great spy missions of American history.” (Aug.)
Jerrold L. Schecter
"Peter Duffy’s Double Agent exposes the shocking extent of German espionage in America on the eve of World War II with dazzling new research and deft historical insight. A riveting non-fiction thriller that exposes history’s neglect of William Sebold, an unjustly forgotten American hero. Duffy offers still relevant insights into the boundaries of civilian surveillance and FDR’s and J. Edgar Hoover’s handling of intelligence information to influence public opinion."
Wall Street Journal
“Intriguing account of the unraveling of the German intelligence network in the U.S.... thrilling.”
"Duffy tracks Sebold’s efforts with a tense, exciting narrative filled with a motley collection of characters, some sinister and some unlikely as villains. This has all the elements of a fine spy novel, with the bonus that it is all true."
The New York Times
“Peter Duffy absorbingly recounts the true story of William G. Sebold… right on target.”
Boston Globe
“Rich with eccentric characters, suspense, and details of spycraft in the war’s early days…. The result is a compelling cultural history with all the intricacy and intrigue of a good spy novel.”
Minneapolis Star Tribune
“Thrilling, well-researched, well-told, fascinating.”
Washington Post
"Double Agent is worth reading."
Pittsburgh Post-Gazette
"Peter Duffy brings out of the cold — well, out of the shadows — a spy who is not only a hero like Bond, but also a man who was never there... Duffy allows the reader not only into the innermost workings of the investigation, but also to connect with the protagonist Sebold and see the aftermath in a truly human hero."
"The intrigues of Sebold and his minders, vividly depicted by Peter Duffy, read at times like a John le Carré novel. There is a gray, dank sense of boredom in a spy's daily existence, along with a frisson of reckless endangerment, both of which Duffy conveys through a plethora of historical detail."
(Hamptons) Dan's Papers
"Double Agent is an important and impressively researched account of a still little-known man who made a big difference in the world of counterintelligence. Duffy reveals new information, much of it from thousands of pages of FBI documents... Both timely and significant."
Chicago Tribune
"The grip of good fiction and the punch of hard truth."
Kirkus Reviews
A sympathetic portrait of a reluctant, little-known German-American double agent on the eve of World War II.There are several spy rings that overlap and converge in journalist Duffy's (The Killing of Major Denis Mahon: A Mystery of Old Ireland, 2007, etc.) immensely readable account, all involving the German immigrant's notion of "patriotism." For many of the select machinists who worked at the Carl L. Norden production facility at 80 Lafayette St. in lower Manhattan, being a good German meant delivering blueprints of the top-secret "bombsight" mechanism to the Abwehr to improve the Luftwaffe's bombing accuracy and thus "save millions and lots of time." Many immigrant laborers were virulently anti-communist and members of the right-wing German American Bund, which paraded openly its support of National Socialism through the streets of the German neighborhood of Yorkville at a time before the FBI, and its emergent director J. Edgar Hoover, had declared the group an internal threat. Yet the other kind of patriotism involved loyalty to one's adopted country, personified by William G. Sebold (1899-1970), who fled the political chaos of Germany in the 1920s and became a naturalized American citizen in 1936. By an extraordinarily unlucky turn of events, when he returned to Germany to visit his mother at the outbreak of war, he was roped into working for the Abwehr in order to get back to the United States. Unbeknownst to the Nazis, he had also contacted the FBI; among the German immigrant community of Yorkville and the Brooklyn Sperry Gyroscope Company, they uncovered a whole nest of subversives offering defense secrets to the Nazis. Sebold ultimately helped to convict 33 traitors in 1941 in what was known as the Duquesne Spy Ring—the first feather in Hoover's hat. While colorful personalities proliferate throughout the narrative, the understated character of Sebold gleams.An entertaining work duly informed by Duffy's knowledge of both the war and New York City.

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Double Agent

  • I have everything I ever wished for, and Germany doesn’t appeal to me a bit.

    —Bill Sebold, in a letter to FBI special agent Jim Ellsworth, August 9, 1946

    In the early afternoon of December 11, 1941, Berlin time, Adolf Hitler mounted the rostrum in the Reichstag and delivered an eighty-eight-minute address that cataloged the sins of President Franklin Roosevelt (an “unsophisticated warmonger” who was “mentally unsound”) and praised the Japanese attack on Pearl Harbor of four days earlier “as an act of deliverance” that “all of us, the German people and, I believe, all other decent people around the world as well,” regard with “deep appreciation.” The Führer took note of “the insulting attacks and rude statements by this so-called president against me personally,” making particular mention of FDR’s barb that he was a “gangster.” “This term did not originate in Europe, where such characters are uncommon, but in America,” he said to the delight of the deputies, assorted Nazi dignitaries, and honored Japanese guests. But the loudest cheers came when Hitler made clear that the purpose of his speech was to declare war on the United States, his voice suddenly drowned out by raucous applause that escalated into a standing ovation.

    Late in the evening on the following day, Brooklyn time, a jury of nine men and three women filed into a packed courtroom in the old federal building on Washington Street. At a few minutes before midnight, the jury’s foreman, Edward A. Logan, stood before the hushed assemblage and read guilty verdicts against the fourteen out of thirty-three Nazi spies who hadn’t already confessed to their membership in what was known as the Duquesne Spy Ring, still to this day the largest espionage case in American history. The proceeding was unmarred by any disruption. “The defendants took the verdicts stoically, for the most part,” wrote the Times. Judge Mortimer W. Byers then thanked Logan and his fellow jurors for their service. “It will readily appear,” he said, “that you have rendered a very substantial contribution to the welfare of the country which you and I hold very dear.” And so they had.

    This, the first US victory of World War II, would’ve been impossible without one man whose contribution to the war effort has never been recognized, William G. Sebold. In a culture that has come to celebrate even the most tangential representation of the Greatest Generation, his identity has remained mysterious, his picture never published. By 1951, Sebold had “lapsed into an obscurity which has been protected ever since by the FBI,” according to a magazine that used a pseudonym to describe him. “All we know is that somewhere in the U.S. today is a tall, gaunt, middle-aged man to whom each native-born American can well doff his hat in love and respect,” neglecting to mention that the non-native-born citizen owed him a debt of gratitude, too. When Sebold died in February 1970, no obituary or death notice appeared in the newspapers. A pivotal figure in America’s confrontation with Nazism had been forgotten.

    ▪  ▪  ▪

    In the years before the formal commencement of hostilities, Hitler’s agents were active in New York. They were a collection of ideologues, opportunists, dupes, adventurers, thugs, sophisticates, poseurs, patriots, seductresses, lackeys, and sympathizers. Most (but not all) were German immigrants who would come to be associated in the public mind (not always unfairly) with a single neighborhood of upper Manhattan, the home base of a nationwide movement of uniform-wearing Nazis whose rallies and marches were a constant source of media fascination. Dwelling within this community of the like-minded were a handful of individuals with the genuine talent to provide meaningful assistance to the German war machine. Few today realize that a Bavarian-born immigrant living in Queens, Hermann W. Lang, succeeded in stealing the plans for America’s greatest prewar secret, a precious instrument of mythic reputation designed to turn modern airplanes into bomb-dropping systems of unprecedented accuracy, a brazen act of thievery that represents the most significant intelligence coup of the Third Reich.

    The spies of the thirties were initially able to conduct their work without worry of detection because the US government, focused on remedying economic misery in a period of rigid isolationism, hadn’t assigned any agency to root them out. The story among the Soviet agents was that you could walk down Broadway wearing a sign identifying yourself as a spy and still not get caught. It took a botched investigation into a portion of the Nazi network in New York by an unprepared FBI to convince President Roosevelt that J. Edgar Hoover should be empowered to become the nation’s first modern spymaster. Already a national celebrity for directing his “G-men” in a tommy-gun-assisted crusade against the John Dillingers and Pretty Boy Floyds of the early Depression, Hoover was given the authority to launch covert investigations against “those who reflect in their pernicious activities the desires of enemy modes of thought and action,” as he said in a speech on October 24, 1939, less than two months after Nazi Germany’s invasion of Poland marked the beginning of the war in Europe.

    But Hoover’s FBI couldn’t rectify the failure to capture the most destructive Nazi agents in New York—and prove that it had the ability to construct a counterespionage operation of sufficient expertise—without Bill Sebold, a naturalized American of German birth who was both guileless and headstrong. In early 1939, he made the mistake of leaving Manhattan and returning to his mother’s home in the Reich just as Hitler was stepping up his march to war. Through “a strange set of circumstances,” as a US diplomat put it, Sebold was coerced into the German espionage service and sent to the United States, accepting the assignment “knowing that he would never go through with it, but knowing that he had to do something in order to get out of Germany alive,” said the FBI. Upon his arrival in New York, he agreed to become the first double agent in Bureau history, the central figure in a pioneering undercover operation that steadily grew in size and sophistication, its expansion enabled by the Germans’ willingness to allow him to reach into an ever-widening circle of Hitler’s underground.

    Under the guidance of the bespectacled special agent assigned to be his handler, Sebold proved to be a gifted improviser and tireless worker possessed of the fortitude to overcome his anxieties and face down some of the most ominous characters in the city. Since neutrality laws and political opposition prevented the Roosevelt administration from providing even limited military assistance to the Allied cause in Western Europe, the case represented our most consequential fight against Fascist aggression during the pivotal years of 1940 and 1941. The double agent, the skilled FBI men brought in from across the country to work with him, and even Hoover himself were among those honored few Americans who actually did something to stop Hitler at a time when national figures such as Charles Lindbergh were arguing for rapprochement. The thirty-three convictions ensured that the enemy could not call upon a small army of embedded loyalists once America joined the war and mobilized its full strength against the Axis. In February 1945, when the death of Nazi Germany was all but guaranteed, the New York Times said the “elimination of this organization, which had extensive ramifications, placed a decisive check on German espionage operations, from which it has found it difficult to recover.” The Manhattan Project to create our greatest wartime secret, the atomic bomb, would be infiltrated by Soviet spies not Nazi ones.

    Sebold became a particularly American kind of hero. He was an immigrant with a less-than-perfect grasp of English who stood in opposition to malignant beliefs from back home that were infecting his ethnic community. He was a brave man forced to endure the charge that he was a traitor to his own people because he regarded his oath of allegiance to the United States, taken when he became a citizen in 1936, as “a sacred thing,” in his description. When one of the accused spies called him a “son of a bitch” in a voice loud enough to be heard throughout the Brooklyn courtroom, an assistant prosecutor approached the bench and confided to the judge, “This Sebold is the kind of a man that throws that kind of thing off like a duck throws water off.” Judge Byers agreed. “Of course he has shown that he has taken his courage right in his hands in this whole thing,” he said out of the hearing of the jury, press, and spectators. “Probably it is nothing new to him to hear people say those things, speak of him that way, but of course it is very distressing from the standpoint of decorum that that should be observed in the courtroom.”

    “As you know,” FBI assistant director D. M. Ladd told Hoover in a memo on December 17, 1945, “Sebold gave us the most outstanding case in the Bureau’s history.”

  • Meet the Author

    Peter Duffy is the author of Double AgentThe Bielski Brothers, and The Killing of Major Denis Mahon. He also works as a freelance journalist and writes regularly for The New York Times, The Wall Street Journal, New York magazine, The New Republic, Slate, and many other outlets. He lives in New York City with his wife and daughter. Visit his website at

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    Double Agent: The First Hero of World War II and How the FBI Outwitted and Destroyed a Nazi Spy Ring 5 out of 5 based on 0 ratings. 1 reviews.
    agcpa More than 1 year ago
    Another great read by Peter Duffy. American Double Agent Bill Sebold was an unsung hero until this book, which brings him to life and finally gives him the credit he deserves, using first-person accounts from personal letters and trial transcripts, and within a richly researched historical context. Manhattan was thick with Nazi spies in the months before WWII, all of them intent on getting their hands on military technologies that could have swung the war, and here's the man who swept them away -- in part by using a hidden camera in an office in Times Square, of all places. Hardly anyone has heard of Sebold. This book should change that. I have to recommend this book to people who enjoy Hoover-era FBI history, WWII bombing and coding secrets, and of course a good spy story.