It was a clear autumn day in Washington, DC on October 27, 1941, when President Franklin Roosevelt delivered his Navy Day speech to the American people. Halloween was later that week, but Adolf Hitler and his Wehrmacht war machine were scaring the administration. Roosevelt used his address to highlight the threat posed to the Western Hemisphere—America’s hemisphere—per the longstanding Monroe Doctrine. The Japanese surprise attack on Pearl Harbor was six weeks hence, and Americans were leery of getting involved again in Europe’s perennially bloody wars. Charles Lindbergh and the “America First” movement, which represented America’s isolationist current, objected to greater involvement. Roosevelt needed to make the case that the Nazi threat to America was real. He noted, earlier that month, that a German U-boat had attacked an American destroyer, the USS Kearny, causing eleven American combat fatalities. “America has been attacked,” Roosevelt declared. “The USS Kearny is not just a navy ship. She belongs to every man, woman and child in this nation. . . . Hitler's torpedo was directed at every American.”

Roosevelt left out the minor detail that the Kearny was busy raining down depth charges on a German U-boat when she was torpedoed. In case the attack on the Kearny wasn’t enough to convince skeptical Americans of Hitler’s devious transatlantic designs, Roosevelt pressed his point with further evidence: “Hitler has often protested,” Roosevelt continued, “that his plans for conquest do not extend across the Atlantic Ocean. But his submarines and raiders prove otherwise. So does the entire design of his new world order,” Roosevelt stated ominously. “For example, I have in my possession a secret map made in Germany by Hitler's government . . . of the new world order.”

“It is a map of South America and a part of Central America, as Hitler proposes to reorganize it . . . into five vassal states, bringing the whole continent under their domination . . . [including] our great lifeline—the Panama Canal. . . . This map,” Roosevelt thundered, “makes clear the Nazi design not only against South America but against the United States itself.”

In addition to millions of Americans tuning their radios in to Roosevelt’s revelations of Nazi treachery, the Germans were listening too. They vociferously denied the authenticity of Roosevelt’s map, but then again, it was marked “Geheim,” (Secret), so of course they would disown it, wouldn’t they? German propaganda minister Joseph Goebbels rejected FDR’s “absurd accusations.” In his estimation, this was a “grand swindle” intended to “whip up American public opinion.” The problem is that Goebbels was right. The map was a forgery. He didn’t know who the real authors were, but British intelligence did—because it was they.

Operating out of the forty-fourth floor of New York’s Rockefeller Center, the remit of the vanilla sounding British Security Coordination office was, in part, to get America into the war. The Roosevelt administration was already reaching across the Atlantic with all sorts of civilian and military aid, but it wasn’t coming fast enough during the dark days of the Blitz, and each new initiative to support the British was met with howls of indignation by the isolationists in Congress. Prime Minister Winston Churchill believed that the Americans would eventually get around to doing the right thing; they just needed a prod in the right direction—a prod in which the ends justified the means.

British intelligence recalled their previous success at stoking America’s ire for war when, in February 1917, desperately seeking American entry into the Great War, they passed the Americans the infamous Zimmermann Telegram, albeit with a phony cover story to hide the fact that they were routinely breaking American diplomatic codes. The Zimmermann Telegram, intercepted and decrypted by British codebreakers, offered a secret deal in which the Germans promised to return New Mexico, Arizona and Texas to Mexico if the latter would declare war on the United States in the event that Washington declared war on Germany.

In that instance, the British artfully used the telegram, authored by German foreign minister Arthur Zimmermann, to overcome characteristic American concern about foreign entanglements. President Woodrow Wilson was in a pickle. Just a year earlier, in the election of 1916, correctly sensing the national mood of nonintervention, he had run and won on the slogan, “He kept us out of war.” Now he felt that war might be inevitable, but how to reverse himself? A week after Wilson received the telegram from the British he authorized its publication in (or, in today’s vernacular, “leaked it to”) the media. It made the front page on March 1, 1917.

Notably, many Americans suspected the dark arts at play, assessing the telegram as a forgery. The wind was taken out of their conspiratorial sails when, two days later, none other than Arthur Zimmermann himself helpfully confirmed that his telegram was genuine. By the next month, America was at war. Not only did the British weaponize the explosive content of Zimmermann’s telegram, but Wilson used it to change tack as well, each to their own political ends.

The Zimmermann Telegram was but one of several factors, including German unrestricted submarine warfare, which led to American entry into World War I. The Americans tipped the balance in favor of the Entente powers and Germany was forced to sign the punitive Treaty of Versailles in 1919, but such a peace could not last, and exactly two decades later the European powers were again at war.

The sequel to the Great War in Europe had been raging since 1939, the German Blitzkrieg seemed unstoppable, and Britain stood alone against it. By late 1941, America had made itself the “arsenal of democracy,” but, as the Kearny incident showed, it actually went much further than that. In addition to Lend-Lease and similar arrangements, American warships and planes patrolled much of the Atlantic convoy route, guarding ships packed with millions of tons of American products—Britain’s tenuous lifeline for survival.

Still, the lost tonnage projections for transatlantic shipping were unsustainable. In a war of material, Britain was going to lose, whereas America’s population and industrial potential were still largely untapped. The supplies sent by America were critical, but if Britain was going to do more than lose slowly, America needed to go all in. But where was the next Zimmermann telegram to help this president lead his country to war? It seemed that, although Britain had affixed keys to every kite it had, lightning was not going to strike twice, but just maybe, this time they could put lightning in a bottle for FDR.

Britain’s senior intelligence official in the United States, Sir William Stephenson, sat atop the British Security Coordination office and became fast friends with Roosevelt’s decorated protointelligence chief, William J. Donovan, acting as coordinator of information, the forerunner of the wartime Office of Strategic Services, itself subsequently reassembled in 1947 as the Central Intelligence Agency. Donovan and Stephenson were birds of a feather. Self-made wealthy men, internationalist in outlook, and both combat heroes of World War I. Stephenson referred to the avuncular and paunchy Donovan as “Big Bill,” and Donovan affectionately labeled the smaller and trimmer Stephenson as “Little Bill.” Years later, Donovan opined, “Stephenson taught us all we ever knew about foreign intelligence”—although perhaps some lessons were learned the hard way.

Despite the bonhomie between the “Bills,” Stephenson was using his friendship with Donovan to run unilateral propaganda operations against the isolationists in American chattering classes. It was in this context that Little Bill handed the fake map (amongst other forgeries) to Big Bill, who presented it to FDR as a cat brings a mouse to its master, perhaps, reminiscent of contemporary news media, not lingering over questions of authenticity because it was a scoop that Donovan had over his rivals in the military branches and J. Edgar Hoover at the FBI.

The State Department, on the other hand, assessed British “intelligence” relating to Latin America as forgeries, even complaining to the British Embassy about it. Assistant Secretary of State Adolf Berle, a man for whom his intelligence portfolio was a bothersome sideshow, was on the right track with his skepticism about the British intelligence that Donovan was feeding to Roosevelt. He had concerns regarding reliability and veracity of the volumes of British intelligence that was finding its way to the Oval Office. Berle told his boss, Secretary of State Cordell Hull, “British intelligence has been very active in making things appear dangerous [in Latin America] . . . I think we have to be a little on our guard against false scares.”

Despite Berle’s suspicions, Roosevelt was not informed of the differing analytical lines in his bureaucracy. In fact, after the Germans cried foul, responding to a question about the map’s authenticity, Roosevelt claimed the source was “undoubtedly reliable.” One scholar pronounced “the most striking feature of the episode was the complicity of the President of the United States in perpetuating the fraud.” Another historian commented that British forgeries like the map were “truly a frontal assault on the rules of evidence.” Yet, like the Zimmermann Telegram twenty-four years earlier, the map served both the author and recipient’s intended political purpose.