The CIA is preparing to declassify hundreds of documents that detail some of its most infamous and illegal operations. The records are believed to cover the period from the 1950s to the 1970s. They include details on domestic spying, infiltrating leftist groups, drug tests on U.S. citizens and assassination plots against foreign leaders. In advance of the release, the National Security Archive has published a new set of documents revealing the Ford administration was concerned about the documents’ eventual disclosure. In a memo to Ford, then-Secretary of State Henry Kissinger said a 1974 article by the investigative journalist Seymour Hersh on the CIA’s infiltration of antiwar groups was “just the tip of the iceberg.” Kissinger also warned that “blood will flow” if several other operations were exposed, including the Kennedy administration’s attempts to assassinate Cuban President Fidel Castro. Kissinger says former Attorney General Robert Kennedy personally managed the assassination plot. Announcing the release on Thursday, CIA Director Michael Hayden said: “Most of it is unflattering, but it is CIA’s history.”