From the document
The United States assumes as a main responsibility the reading of Japanese military and air traffic; the British assume a like responsibility for German and Italian military and air traffic.
This agreement, when implemented, will enable us to fulfill our immediate needs for special intelligence from these sources and will safeguard our long term interests by allowing us to gain the experience required for achieving independence in this field.
Since it is believed unnecessary and impracticable to duplicate work on German machine ciphers and in view of the large number of personnel required and the unavoidable extra risk to the security of the source involved, agreement which follows has been arrived at.
if from any document that might fall into the hands of the enemy or from any message that the enemy might intercept, from any word that might be revealed by a prisoner of war, or from any ill-considered action based upon it, the enemy were to suspect the existence of the ULTRA source, that source would probably forever be lost to our cause.
Excerpts are passages from a US government work (public domain), quoted exactly as read at this copy.
Twelve typed pages. The first is an American staff paper: a memorandum of 10 June 1943 from the Military Intelligence Division (G-2) of the War Department General Staff to the Army Chief of Staff, asking him to approve an agreement already signed with the British. The pages behind it are that agreement, dated 17 May 1943, with two appendices; the second appendix is Britain's own rulebook for handling Ultra1. It is the Army's half of what became known as BRUSA, the wartime arrangement that preceded the UKUSA signals intelligence agreement of 19462,5.
Who wrote and signed what
The covering memorandum is a US document. It carries the MID letterhead and is signed by Maj. Gen. George V. Strong, Assistant Chief of Staff, G-2, who describes the attached paper as an original copy "signed by E. W. Travis, Deputy Director (Services), G.C. and C.S., acting for the British Chiefs of Staff, and by the undersigned, acting for the Chief of Staff, U.S. Army." Lt. Gen. Joseph T. McNarney, Deputy Chief of Staff, approved it "by order of the Secretary of War" on 15 June 19431.
The agreement itself was a joint text, negotiated with the Government Code and Cypher School (GC&CS) at Bletchley Park. Its last page bears Strong's signature and Travis's, with the date "1st March 1943" typed above them at the foot of the British regulations, and McNarney's approval stamp of 15 June1. Strong had been pressing for cryptanalytic exchange since he raised it with the British Chiefs of Staff as a brigadier general in London in August 19404. Wikipedia, drawing on Stephen Budiansky, links the final deal to an April 1943 visit to Bletchley Park by Alfred McCormack, Telford Taylor and William Friedman6.
What the agreement says
Sixteen numbered clauses cover the "detection, identification and interception" of signals and the solution of codes and ciphers of the Axis army and air forces, including the Abwehr; enemy diplomatic, naval and neutral traffic were left for later talks. America took main responsibility for Japanese army and air systems, Britain for German and Italian. The two sides would warn each other at once of any sign that one of their own ciphers was compromised, and neither would downgrade the other's material1.
The agreement also sets out the categories. "Special Intelligence A", from the hardest high-grade ciphers, went only to "the most highly placed officers"; "Special Intelligence B", from lower-grade systems, could be used tactically1.
Appendix A deals with German machine ciphers, meaning Enigma. Rather than duplicate Bletchley's work, the War Department would receive the intelligence; US liaison officers at GC&CS would choose what went to Washington; a US party in Britain would learn by breaking keys itself on British machines; and Ultra would reach American commanders through special British units, with a US officer trained at Bletchley attached wherever an American was commander-in-chief. On security questions the Director of GC&CS kept "the final decision"1.
Appendix B is the British rulebook: Ultra messages for army and air commanders and their senior staff only, burned after use, never passed to lower formations as such, and never acted on against a ship or target unless reconnaissance had also been flown to provide cover1.
Afterlife and release
The Army got what Strong's memo promised, a share in the product now and the experience to stand on its own later1. The 1946 UKUSA agreement, at first also called BRUSA, carried the wartime arrangements into peacetime3,5. On Ultra and the breaking of Enigma and the US Army, see also the TICOM synopsis.
NSA declassified this copy on 7 April 2010 and released it with the UKUSA papers on 24 June 2010, in coordination with GCHQ1,3. The scan is complete, with no redactions. It records what was agreed and signed, not how the arrangement worked in practice; for that, and for the frictions NSA's historians describe, other sources are needed4.
Sources
- NSA Agreement between British Government Code and Cipher School and U.S. War Department in regard to certain 'Special Intelligence', 10 June 1943 (DOCID 3678774), National Security Agency (1943-06-10).
- NSA UKUSA (Historical Releases), National Security Agency.
- NSA Declassified UKUSA Signals Intelligence Agreement Documents Available (press release, 24 June 2010), National Security Agency (2010-06-24).
- Official history The International Agreements, National Security Agency, Center for Cryptologic History (2021-08-20).
- Official history A Brief History of the UKUSA Agreement, GCHQ.
- Wikipedia 1943 BRUSA Agreement, Wikipedia.