Sign in
Government & LawWorld Wars and the Atom

Operation Shamrock

1945Claims checked

From 1945 to 1975 the major telegraph companies secretly handed copies of international telegrams to U.S. intelligence, letting the NSA read millions of messages sent by Americans.

The story

During World War II, military censors read international cables leaving the United States. When the war ended in 1945, the Army asked the big telegraph companies, RCA Global, ITT World Communications and Western Union, to keep giving it copies of international traffic, and they agreed in secret. The program, code named Shamrock, passed to the National Security Agency when it was created in 1952. By the 1960s, NSA staff were picking up magnetic tapes of the day's telegrams in New York and sorting them by computer, and at its peak analysts reviewed about 150,000 messages a month.

Shamrock had no warrant or law behind it, and successive presidents and attorneys general were barely aware of it. The Church Committee uncovered it in 1975, calling it probably the largest government interception program affecting Americans ever undertaken, and NSA Director Lew Allen ended it that May. Together with Project MINARET, its exposure led Congress to pass the Foreign Intelligence Surveillance Act in 1978, which required court approval for national security wiretaps on Americans.

Why it mattered

  • Shamrock's exposure was a main reason Congress passed the Foreign Intelligence Surveillance Act in 1978.
  • The arrangement with private carriers became a precedent for later secret cooperation between telecom companies and the NSA after 2001.
  • It showed how a wartime emergency power could quietly continue for decades without legal authority.

Sources

  1. Spying on the Home Front: Telecoms PBS Frontline
  2. Interception of International Telecommunications by the National Security Agency Georgetown Law
  3. Time of Investigations (Cryptologic Almanac 50th Anniversary) National Security Agency
  4. Spying on the Home Front: The Church Committee and FISA PBS Frontline

Drafted by AI (Claude) from the sources above and checked against them by AI; no historian has reviewed this page. Spot a mistake? Suggest a correction. How pages are made

Claims checked against the record

Consensus: The Church Committee's 1975 to 1976 investigation documented Shamrock in detail. It is one of the clearest cases of mass warrantless surveillance of Americans.

Telegraph companies secretly gave the government copies of international telegrams for 30 yearsEstablished
The Church Committee obtained testimony and records from the NSA and the companies, and the NSA director confirmed the program in 1975.
Read this view
Shamrock was illegalEstablished
The program operated without warrants and violated the Communications Act's privacy protections, as the Church Committee concluded. No one was prosecuted, partly because the Justice Department declined to bring charges.
Read this view
Shamrock led directly to the Foreign Intelligence Surveillance ActEstablished
Legislators cited Shamrock and MINARET when drafting FISA in 1978 to put national security wiretaps under court supervision.
Read this view
Telecom cooperation like Shamrock resumed after 2001Established
Later investigations showed carriers again provided the NSA access to communications under Stellar Wind, a parallel journalists and Congress noted at the time.
Read this view

Community notes

Loading notes…

Learn more ranked by votes

BookJames Bamford
The Puzzle Palace
Editor's pick
BookJames Bamford
Body of Secrets
Editor's pick
VideoSearch on YouTube
Operation Shamrock NSA telegrams Church Committee documentary
Editor's pick