June 29, 2019 marked the 70th anniversary of CANUSA, the 1949 agreement between Canada and the United States that laid the foundations for sharing signals intelligence between our two nations. 

The first seeds of CANUSA were planted during the Second World War, when the United Kingdom requested German signals traffic from the (then neutral) United States.  Canada, because of its strategic location, became a natural partner in this wartime endeavour.

Canadian SIGINT, from both civilian and military cryptologic agencies, proved to be valuable beyond expectations to this wartime partnership, with Canada providing vital intelligence related to South American, French, Spanish, and Japanese traffic, and the Battle of the Atlantic.

Intelligence sharing throughout the war was a significant advantage to the Allies.  As the war came to an end, the UK and US began earnest negotiations to maintain their partnership and formalize a post-war intelligence-sharing regime.

The result was the BRUSA (Britain-USA)* agreement of March 5, 1946.  The status of British dominions in this agreement, including Canada, Australia, New Zealand, and others, was dealt with in the agreement’s appendices.  These countries, though playing an important role, were meant to be junior partners.

It was clear early on, however, that neither Canada nor the United States was satisfied with the requirement for UK approval before sharing SIGINT information bilaterally.  Negotiations soon began to fortify Canada’s role in this new intelligence partnership.

Canada had emerged from the Second World War with a stronger national identity and a desire to play a larger role on the world stage; this ambition would require an independent appraisal of world affairs and the ability to set and pursue national intelligence priorities.

Canada sought an equal seat at the table in the emerging post-War intelligence alliance.

After three years of negotiations, an exchange of letters began between Canadian and US SIGINT authorities on May 27, 1949.  G.G. (Bill) Crean, Chairman of the Canadian Communications Research Committee (CRC) proposed a bilateral arrangement on the security and sharing of COMINT with the United States Communication Intelligence Board (USCIB).  

Major General Charles Cabell, Chairman of the USCIB formally accepted the proposal in a letter sent on June 29, 1949.  With this, CANUSA was born, representing Canada’s equal partnership in the broader BRUSA agreement.

Seventy years on, the CANUSA agreement has deepened and matured, and proven its worth many times over. CSE remains proud to be part of the Five Eyes Partnership and recognizes the foresight and achievements of our predecessor organizations in paving the way for this enduring intelligence alliance.

* In 1952, BRUSA was retroactively renamed UKUSA, as “Britain” is used only with Commonwealth countries, and “United Kingdom” with all others.

Find the agreement, in full here.

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