Here is an interesting article by an American counter-espionage agent who tells several stories about the various Japanese spies he had encountered during the early months of the war. He wrote of his his frustrations with the civil liberty laws that were in place to protect both citizen and alien alike.
It was Mexican president Manuel Avila Camacho who chased the spies out of his nation - click here to read about it...
When the twenty-year-old editor at Yank Magazine wrote this editorial at the close of W.W. II he was expressing a belief that was shared equally with the members of the W.W. I generation who prosecuted and managed the war from Washington - and that was an understanding that the world is a far more dangerous place than we thought it was and it needs to be watched. This 1946 article is similar to other columns that appeared in 1947 (when the CIA was established) and 1952 (when the NSA opened its doors) in that it announced the creation of a government agency intent on global espionage in order to have done with all future concerns that another Pearl Harbor was in the planning.
A 1939 magazine article that reported on the assorted activities of Japanese spies operating around the Tijuana/San Diego region (their presence was well-documented by the Mexican military in addition to the F.B.I.).
A year and a half before the Pearl Harbor attack, Naval Intelligence sold a Japanese agent some bogus plans of the naval installation - more about this can be read here.
This is the story of Harry Sawyer (real name William G. Sebold), a German immigrant to American shores. On a return trip to Germany to visit family in 1939, Sawyer was very reluctantly forced into service as a spy for the German SD (Sicherheitsdienst), the intelligence arm of Himmler's SS. Sawyer was schooled briefly in the ways of spying, told what was expected of him and then let loose to set sail home.
Upon his return, Sawyer quickly explained his problem to J. Edgar Hoover, who masterfully turned the situation to his advantage, an advantage that led to the capture of 32 Nazi spies.
Click here to read about "Lucy" - Stalin's top spy during the Second World War. The story of the German master spy who grimly plotted for sixteen years to destroy the pride of the British Navy... "This is the story of how Russia got military secrets from the United States during W.W. II. It is a story that has little to do with the spy ring that congressional committees are trying to prove existed during the war period (The Gouzenko Affair: read about it here) . But it does throw light on the methods and purposes of the so-called 'spy ring'". "Military information was going to Russia as a matter of routine, by official channels, on an organized basis, all during the period when United States Communists and their friends were supposed to be spying out bits of information to send... As an ally of the U.S. in the war against Germany, Russia had free access to far more information than the so-called 'spy ring' claims..." | 
