If we were to talk about the unsung heroes during World War II, then we must not be remiss in giving credit to the librarians and researchers whom the US government recruited to become, essentially, the first intelligence officers and agents before the establishment of the CIA.
And if the British had Alan Turing who helped intercept German messages, the US had Adele Kibre among the cadre of librarian recruits to gather Nazi publications which proved crucial in gathering vital information during the war. It is said that her acquisition of periodals such as Zeitschrift für Physik and Die Naturwissenschaften helped the scientists involved in the Manhattan Project to develop the nuclear bomb ahead of the Nazis.
Apart from this, the librarians and researchers of the Interdepartmental Committee for the Acquisition of Foreign Publicatioins (IDC), developed networks and ties with other resistance forces throughout Europe which helped them smuggle the periodicals to the US. After publications were ceased, they turned to human sources by interrogating prisoners of war and other Allied sympathizers.
Joining forces with the British army, they rummaged through abandoned Nazi territories and bombed-out bookstores, as well as confiscating books that could have been used to spread genocidal messages, or to harbor other information such as military weaponry. In the end, all these materials had become US properties where they were stored in universities and other cultural organizations.
(Image credit: Smithsonian Institution/Public Domain, Wikimedia Commons)