In 1946-47, the United Kingdom, Canada, Australia and New Zealand (represented by Australia) founded the Commonwealth SIGINT Organization under the leadership of GCHQ.  Around the same time, in 1947 or 1948, the United Kingdom and the United States signed the UKUSA Agreement (which, according to one source, « actually consists of a series of joint agreements, exchanges of letters and memorandums of understanding »).  These two developments marked the formal creation of the siGINT community of the post-war period.  Brigadier General Walter Agee, USAF, Deputy Director of secret services, « Memorandum for the Coordinator of Joint Operations: Proposed U.S.-Canadian Agreement, » June 7, 1948. It seems likely that these elements were not substantially altered in the final version of the agreement.  The Ties That Bind, 142. Although most sources date back to the UKUSA agreement in 1947, some sources have recently suggested that it actually dates back to 1948. See, for example, « The Growth of the Australian Intelligence Community and the Anglo-American Connection, » S. 223-224, and Peter Wright, Spycatcher: The Candid Autobiography of a Senior Intelligence Officer, Stoddart, 1987.
June 29, 2019 marks the 70th anniversary of CANUSA, the 1949 agreement between Canada and the United States, which laid the groundwork for signal-sharing between our two nations. Seventy years later, the CANUSA agreement has deepened and matured and proven its worth. CSE remains proud to be a member of the Five Partnership Eyes and commends the foresight and achievements of our predecessors in paving the way for this permanent intelligence alliance. The new policy, implemented by mutual agreement between the two countries, means that people will not be able to cross the Vermont-Quebec border for recreation and tourism. A number of ancillary agreements govern the Community`s role in areas such as the division of labour for the SIGINT collection, safety standards, etc. The division of labour would be indicated in a protocol called siGINT Combined Operating List (SCOL).  According to Jeffrey Richelson and Desmond Ball, « the current division of jurisdiction attributes coverage of the Eastern Indian Ocean and parts of Southeast Asia and the Southwest Pacific to DSD; Africa and the Soviet Union east of the Urals to GCHQ; the northern USSR and parts of Europe at the Canadian ETS; a small part of the Southwest Pacific to the New Zealand GCSB; and all other areas of interest to the NSA and its component services. As Richelson and Ball put it, « the geographical division of the world is obviously not as clear in practice. »  The NSA, for example, dominates the mission of the SIGINT collection in the former Soviet Union. Nevertheless, the CSE`s contribution to SIGINT`s collection and analysis of the former Soviet Union remains significant. (c) each authority will seek the agreement of the other authority on all measures taken with third parties and will not take such measures until its jurisdiction has been agreed by both authorities. The agreement of the other, once obtained, will be left to the person concerned to implement the measures agreed in the most appropriate way, without it being possible to indicate precisely by which channels it will be possible to proceed. Member organisations of the UKUSA community include the Communications Security Establishment, the US National Security Agency (NSA), the UK Government Communications Headquarters (GCHQ), the Australian DSD (DSD) and the New Zealand Government`s Communications Security Bureau.
A number of SIGINT agencies from other countries also participate in the UKUSA community, including those in Germany, Japan, Norway, South Korea and Turkey. These countries are sometimes referred to as « third parties » to the agreement.  In addition, some countries, such as China, SIGINT UKUSA or SIGINT stations share SIGINT on a more limited basis.