The British Joint Staff Mission in Washington was set-up following a series of Anglo-American talks in London during the summer and autumn of 1940, to discuss methods of bringing about close military co-operation between the two nations should the United States enter the war. Agreement on concerted plans was reached and, in addition, military missions were to be exchanged. Further conversations took place in Washington during the first four months of 1941 on the composition and scope of the missions, after which a 'nucleus' mission in Washington was established in June 1941.
The Mission was responsible to the Chiefs of Staff Committee, and was headed by three very senior officers from each of the Services who also headed the single Service missions which were established at this time. Each also represented his Chief of Staff in contacts with US Chiefs of Staff and other highly placed US officials (civil as well as military). The Washington mission also advised the ambassador and British supply missions in the United States on strategic and other important military questions.
The Secretariat to the Chiefs of Staff was part of the British Joint Staff Mission, and from 1946 reported directly to the newly created Ministry of Defence.
In 1947, it was agreed that where possible, individual missions in Washington should be abolished, and any necessary responsibilities absorbed into the British Joint Staff Mission. On 12 January 1948, the three single Service missions became the naval, military and naval components of the British Joint Staff Mission (the Navy Staff, the Army Staff, and the Air Force Staff), together with a fourth component, Technical Services, which reported to the Ministry of Supply. From this date, the Mission became known as the British Joint Services Mission.
In reality the status and methods of operation of the Staffs were unchanged. Initially, the Ministry of Defence was comparatively small and did not include the Navy, Army and Royal Air Force, which each had their own representatives at Cabinet level, with the Cabinet Secretariat apparently continuing to receive minutes of meetings, memoranda, and working papers from the Mission's Washington Office.