This date in history: BRUSA signed

On this date in history, 17 May 1943, the BRUSA agreement was signed by Britain and the United States. The direct forerunner of the 1946 BRUSA agreement (which was renamed the UKUSA agreement in 1954), the 1943 agreement formalized wartime communications intelligence cooperation between Britain's Government Code and Cipher School (later known as GCHQ) and the U.S. Army's Signal Security Agency. The "Holden agreement" of 2 October 1942, also a forerunner of the UKUSA agreement, had earlier laid out the parameters of British-American naval COMINT cooperation.

The text and appendices of the BRUSA agreement were released to the public in 1995 and were published in the journal Cryptologia in 1997 ("The BRUSA Agreement of May 17, 1943," Cryptologia, vol. 21, no. 1 (Jan. 1997): 30-38).

[Update 28 May 2009: Details of post-war BRUSA/UKUSA agreement updated to reflect more recent information.]