Cullather was recruited by the CIA as a graduate student in 1992 to investigate documents pertaining to PBSuccess, the operation that led to the 1954 Guatemalan coup d'état, as part of a larger review meant to determine which documents could be declassified. The result of that study was "Secret History: The CIA's Classified Account of Its Operations in Guatemala, 1952-1954". Many of the documents discussed in the book had already been publicized by Philip Agee and others; Cullather's study, "the facsimile reproduction of an internal agency study", was released in 1997 before the CIA, in mid-1998, "aborted the entire declassification process". Cullather's study, according to Lars Schoultz, is "an exceptionally valuable document-not simply a lucid chronicle of who did what to whom, but a vivid cautionary tale about how the cloak of secrecy allowed government officials to avoid questions of perspective, of proportion, and of right and wrong". Historian Greg Grandin called it "an extremely important scholarly and pedagogical work".