In August 1940, the Dies Committee heard from a witness named Henry Hoke, a professional advertiser who ran the publication The Reporter of Direct Mail Advertising. Hoke was alerted to the growing Nazi threat in the US when his college-aged son showed him pro-Nazi flyers that were passed out at his school. Being in advertising, Hoke recognized them as propaganda. Over the next six months, Hoke collected more examples of Nazi propaganda, and he published his findings in a long exposé in The Reporter of Direct Mail Advertising. He named the organizations behind this propaganda campaign—including The German Library of Information, The German Railroads Information Office, and the German Board of Trade—and tallied their outputs; collectively, they were publishing hundreds of thousands of pieces of propaganda to disseminate throughout the US. Hoke was struck by the campaign’s well-financed, strategic, and sophisticated nature.

Despite receiving threatening letters at his home, Hoke continued in his efforts. After he published his exposé, citizens from across the country started sending him more examples of propaganda. Hoke attempted to alert various authorities about the Nazis’ campaign, including the postmaster general of the US, but the postal inspectors told Hoke they could not act because none of what Hoke had found was against the law.