German obituary notices published in local newspapers proved a goldmine for R&A economists. Little did the editors of Germany’s small town newspapers know that they were betraying Nazi manpower secrets.

R&A analysts collected as many obituaries for deceased German troops as possible, according to a declassified OSS history, which the agency used to create a representative sampling of German casualties based on newspaper circulation rates.

By applying the ratio of officer-to-enlisted casualties among German troops during World War I, and the ratio of captured to killed and wounded, R&A managed to reconstruct German military personnel losses.

No piece of information, however seemingly innocuous, was too obscure for R&A analysts. OSS sent R&A economists to Europe to survey the vehicle wreckage the Germans left behind on the battlefield.

The Germans, notoriously meticulous record-keepers, had dutifully stamped their tanks with serial numbers. When properly assembled and analyzed, the serial numbers yielded estimates of total Germany’s total tank production.

When information gaps existed in the government’s existing intelligence, R&A looked to the sources right under their noses to fill in the blanks. In 1942, Donovan created the Enemy Objectives Unit, a collection of R&A economists tasked with helping the U.S. Eighth Air Force select German industrial targets that would cause maximum chaos if destroyed.

Neither the military nor the OSS had the intelligence necessary to understand fully how German factories operated and, by extension, how their losses could affect military production.

So EOU economists simply sought out British factories which closely resembled their German counterparts. The tours and interviews gave them the information necessary to select the most devastating targets for Allied bombers.

R&A’s work earned the respect of the military. Shortly before the American invasion of North Africa, R&A analyst Sherman Kent, a post-war legend in the CIA for his pioneering analytical skills, crunched on a last minute study of railways and communications lines, drawn largely from open sources and materials available in the Library of Congress.

The open-source intelligence analysts of World War II had a huge advantage unavailable to their predecessors in previous wars thanks to the changing media landscape of the 1930s and ’40s.

Back then, shortwave radio occupied a role similar to the Internet today. As radio became a popular news and entertainment medium, countries increasingly used it for broadcasting propaganda.

Shortwave broadcasts could reach audiences further away, providing a global megaphone for any country that wanted to persuade and intimidate abroad.

American news outlets like the International Herald Tribune, NBC and CBS set up listening stations to stay on top of the boiling tensions in Europe—and academia followed suit.

Princeton University established the first organizational effort in the United States to analyze the glut of foreign propaganda broadcasts in 1939. Harold Graves, head of the Princeton’s Listening Center, was quick to see the intelligence value of such broadcasts.

He published a book on the subject, War On The Short Wave, which heralded broadcasting as a “fourth front” in war, next to politics and economics.

Graves walked readers through the bounty of official programming coming from countries like Germany, France and the Soviet Union, illustrating how broadcasts from the “wordiest war in history” yielded subtle clues about intentions and circumstances abroad.