Room 40

Room 40 was the United Kingdom's communications intelligence analysis center in the First World War. It later became part of the Second World War Government Code and Cipher School in Bletchley Park, which, in turn, became the Government Communications Headquarters, the U.K. equivalent of the U.S. National Security Agency.

Among the major accomplishments of Room 40 was the decryption of the Zimmerman telegram, which had a large role in bringing the United States into the war.