Andrew Coddington 
Code Breakers and Spies of the Vietnam War [PDF ebook] 

Set against the backdrop of the Cold War, the conflict in Vietnam was much more than a battle between Vietnamese and American forces. Although the fighting may have taken place in monsoon-swept cities and booby-trapped jungles, the Vietnam War was fought on a much larger scale. Spies were active on all fronts, including within the United States itself. Readers will explore how technology and tactics not only shaped the Vietnam War, but changed the ethics of American surveillance from then until the present day.