I put this post under a thread with the identical title, only after I posted, did I realize it was under the Gettysburg area. So I am copying it here where it may be more appropriate:
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I've just started
Grant's Secret Service by William B. Feis.
It's focused on Grant's use of all sorts of sources of information, not strictly scouts and spies. It's sort of like a 'what did he know, and when did he know it' sort of examination of Grants campaigns.
Very good, so far, and it has just about the best maps I have ever found in a non-topographically oriented CW book.
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Check out these CIA web pages about "Intelligence in the Civil War"
https://www.cia.gov/cia/publications.../Civil_War.htm
See the BMI section: The Bureau of Military Information section is of particular interest.
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