Above is a photograph of Commander Joseph Wenger, the senior American naval codebreaker who led the American team negotiating the revised BRUSA agreement in London in March 1946. His main negotiating partner was Sir Stewart Menzies. This agreement was the first in which the United States entered into a consolidated national agreement with the British rather than using separate agreements between Britain and the US Army or the US Navy. It provided an exchange of traffic. communications documents and equipment, traffic analysis and cryptanalysis information, decryption and translation data, and information relating to all aspects of communications organization, practices, procedures, and equipment. It was signed by Colonel Patrick Marr-Johnson on behalf of the London Signals Intelligence Board and Lt General Hoyt S Vandenberg on behalf of the State-Army-Navy Communication Intelligence Board (STANCIB). Patrick Marr-Johnson subsequently became Britain's first post Senior UK Liaison Officer in Washington (SUKLO).
Officially it is claimed that the 1946 BRUSA agreement -
1. Defines communications intelligence
2. Establishes the full exchange of the “products” of communications intelligence and the methods used to obtain it.
3. Excludes the communications of any of the partners from the exchange
4. Establishes mechanisms for notifying the other partners if and when information will be withheld but attempts to limit these occasions to a minimum
5. Prohibits the use of communication intelligence for commercial purposes
6. Places limits on telling ‘third party’ countries about the existence of the agreement and precludes unilateral action with third parties on any subject pertaining to communications intelligence.
7. Makes clear that the agreement supersedes all previous agreements between US and British authorities while establishing that either party can terminate the agreement should they consider it in their interests to do so.
However, some of these clauses were observed in the breach. Britain and the United States exchanged almost 100% of their material on the Communist Bloc - with a strong focus on military targets. In practice exchange was more selective on regions like the Middle East where the policies of London and Washington could be out of step. K Division, which handled non-Soviet targets, did much less business with the Americans than J Division. GCHQ and NSA both used comint for economic purposes and here there was little exchange. The UK sometimes told Third Parties more than the USA wished about UKUSA. Some researchers suspect that there was intermittent examination of UK communications by the USA in the early 1970s, but this is unconfirmed.
Other second parties joined in the decade followng the 1946 BRUSA agreement, for example Canada in 1949, using an agreement that was similar in structure to that between the UK and USA. BRUSA changed its name to UKUSA at the request of the British in 1954. UKUSA continues to evolve and it has been rumoured that Israel achieved de facto second party status in recent years.
For a more detailed discussion of BRUSA and UKUSA see -