In the spring of 1940, British Prime Minister Winston S. Churchill was certain of one thing for his nation caught up in a fight to the death with Nazi Germany: Without American support his nation might not survive. But the vast majority of Americans—better than 80 percent by some polls—opposed joining the fight to stop Hitler. Many were even against sending any munitions, ships or weapons to the United Kingdom at all. To save his country, Churchill had not only to battle the Nazis in Europe, he had to win the war for public opinion among Americans. He knew just the man for the job.

In May 1940, as defeated British forces were being pushed off the European continent at Dunkirk, Churchill dispatched a soft-spoken, forty-three-year-old Canadian multimillionaire entrepreneur to the United States. William Stephenson traveled under false diplomatic passport. MI6—the British secret intelligence service—directed Stephenson to establish himself as a liaison to American intelligence. He went to the White House where the President, Franklin D. Roosevelt, remained deeply concerned about the fate of Great Britain. To Stephenson’s dismay, he learned that the U.S. government had no coordinated central command for spies and counterintelligence. Stephenson would have to create one on London’s behalf in America. Before long, Britain’s lone secret agent in the Americas built a vast clandestine propaganda, counterintelligence, and espionage empire.

Few men were ever so well equipped for cloak-and-dagger work. Stephenson’s life and lore were right out of a book—and before long would become one. Short, thickly muscled as befitted a former boxing champion, with cropped graying hair, hooded, penetrating eyes, and forward-thrusting chin, he had dropped out of high school in Canada and eventually joined the Royal Flying Corps in World War I. An air Ace, he was credited with twelve combat kills. After being shot down, wounded and captured, he made a daring escape from a German prison camp. At the outbreak of the Second World War, he had approached his friend Churchill with the offer to go to Berlin to assassinate Hitler. Before sending him to the U.S., Churchill codenamed him, “Intrepid.”