Project E was a joint project between the United States and the United Kingdom during the Cold War to provide nuclear weapons to the Royal Air Force (RAF) until sufficient British nuclear weapons became available. It was subsequently expanded to provide similar arrangements for the British Army of the Rhine. A maritime version of Project E known as Project N provided nuclear depth bombs used by the RAF Coastal Command.
The British nuclear weapons project, High Explosive Research, successfully tested a nuclear weapon in Operation Hurricane in October 1952, but production was slow and Britain had only ten atomic bombs on hand in 1955 and fourteen in 1956. The prime minister of the United Kingdom, Winston Churchill, approached the president of the United States, Dwight D. Eisenhower, with a request that the US supply nuclear weapons for the strategic bombers of the V bomber fleet until sufficient British weapons became available. This became known as Project E. Under an agreement reached in 1957, US personnel had custody of the weapons, and performed all tasks related to their storage, maintenance and readiness. The bombs were held in secure storage areas (SSAs) on the same bases as the bombers.
The first bombers equipped with Project E weapons were English Electric Canberras based in Germany and the UK that were assigned to NATO. These were replaced by Vickers Valiants in 1960 and 1961 as the long-range Avro Vulcan and Handley Page Victor assumed the strategic nuclear weapon delivery role. Project E weapons equipped V-bombers at three bases in the UK from 1958. Due to operational restrictions imposed by Project E, and the consequential loss of independence of half of the British nuclear deterrent, they were phased out in 1962 when sufficient British megaton weapons became available, but remained in use with the Valiants in the UK and RAF Germany until 1965.
Project E nuclear warheads were used on the sixty Thor Intermediate Range Ballistic Missiles operated by the RAF from 1959 to 1963 under Project Emily. The British Army acquired Project E warheads for its Corporal missiles in 1958. The US subsequently offered the Honest John missile as a replacement. They remained in service until 1977 when Honest John was superseded by the Lance missile. Eight-inch and 155 mm nuclear artillery rounds were also acquired under Project E. The last Project E weapons were withdrawn from service in 1992.
Background During the early part of the Second World War, Britain had a nuclear weapons project codenamed Tube Alloys. At the Quebec Conference in August 1943, the prime minister of the United Kingdom, Winston Churchill, and the president of the United States, Franklin Roosevelt, signed the Quebec Agreement, which merged Tube Alloys with the American Manhattan Project to create a combined British, American and Canadian project. The September 1944 Hyde Park Aide-Mémoire extended commercial and military cooperation into the post-war period. Many of Britain's top scientists participated in the Manhattan Project. The Quebec Agreement specified that nuclear weapons would not be used against another country without mutual consent. On 4 July 1945, Field Marshal Sir Henry Maitland Wilson agreed on Britain's behalf to the use of nuclear weapons against Japan.
The British government considered nuclear technology to be a joint discovery, and trusted that America would continue to share it. On 16 November 1945, President Harry S. Truman and Prime Minister Clement Attlee signed a new agreement that replaced the Quebec Agreement's requirement for "mutual consent" before using nuclear weapons with one for "prior consultation", and there was to be "full and effective cooperation in the field of atomic energy", but this was only "in the field of basic scientific research". The United States Atomic Energy Act of 1946 (McMahon Act) ended technical cooperation. Its control of "restricted data" prevented US allies from receiving any information. Fearing a resurgence of American isolationism, and Britain losing its great power status, the UK government restarted its own development effort, now codenamed High Explosive Research.
In 1949, the Americans offered to make atomic bombs in the US available for Britain to use if the British agreed to curtail their atomic bomb programme. This would have given Britain nuclear weapons much sooner than its own target date of late 1952. Only those bomb components required by war plans would be stored in the UK; the rest would be kept in the US and Canada. The offer was rejected by the British Chiefs of Staff on the grounds that it was not "compatible with our status as a first class power to depend on others for weapons of this supreme importance". As a counter-offer, they proposed limiting the British nuclear weapons programme in return for American bombs. The opposition of key American officials, including the United States Atomic Energy Commission's Lewis Strauss, and Senators Bourke B. Hickenlooper and Arthur Vandenberg, coupled with security concerns aroused by the 2 February 1950 arrest of the British physicist Klaus Fuchs as an atomic spy, resulted in the proposal being dropped.
Negotiation The first British atomic bomb was successfully tested in Operation Hurricane; it was detonated on board the frigate anchored off the Monte Bello Islands in Australia on 3 October 1952. The first Blue Danube atomic bombs were delivered to the Royal Air Force (RAF) Bomber Command Armaments School at RAF Wittering on 7 and 11 November 1953, but the RAF had no bombers capable of carrying them. The first production order for 25 Vickers Valiants was issued on 9 February 1951, and they were delivered on 8 February 1955.
Once production of V-bombers began in earnest, their numbers soon exceeded that of the available atomic bombs. Production of atomic bombs was slow, and Britain had only ten on hand in 1955, and fourteen in 1956. At this rate, there would not be sufficient bombs to arm all the V-bombers until 1961. At the three-power Bermuda Conference with President Dwight D. Eisenhower in December 1953, Churchill suggested that the US allow Britain access to American nuclear weapons to make up the shortfall. There were several technical and legal issues. For American bombs to be carried in British aircraft, the US would have to disclose weights and dimensions, while their delivery would require data concerning their ballistics. The release of such information was restricted by the McMahon Act. There would also be issues of custody, security and targeting.
In May 1954, the Vice Chief of Staff of the United States Air Force (USAF), General Thomas D. White, approached the head of the British Joint Staff Mission (BJSM) in Washington, DC, General Sir John Whiteley, with an offer to provide the RAF with an interim force of up to 90 new Boeing B-47 Stratojet bombers. This represented about $400 million in equipment that would not be counted against the Mutual Defense Assistance Program. The RAF was wary. The B-47 was judged inferior to the English Electric Canberra although it had greater range and could carry a larger bomb load. It would require runways, and the RAF had had a bad experience with the last American-built bomber it operated, the Boeing Washington. Above all, there was the potential loss of prestige and independence. The head of RAF Bomber Command, Sir Hugh Lloyd, favoured acceptance, but the Secretary of State for Air, Lord de L'Isle and Dudley, and the Minister of Supply, Duncan Sandys, advised Churchill against it. In June, the Chief of the Air Staff, Sir William Dickson, informed the Chief of Staff of the United States Air Force, General Nathan Twining, that the RAF was declining the offer.
In the lead-up to Churchill's next meeting with Eisenhower in June 1954, the president's assistant for atomic energy, Major General Howard G. Bunker, discussed carriage of American atomic bombs in British aircraft with the BJSM. A detailed list of the equipment and technical data required was drawn up, and the USAF undertook to provide training and technical assistance, and to establish facilities to store, assemble and assist with loading the bombs. The McMahon act was amended in August 1954, and while it did not go nearly as far as the British government wanted—the transfer of information regarding the design and manufacture of nuclear weapons was still prohibited—it did now allow for the interchange of information on their use. This paved the way for the Agreement for Cooperation Regarding Atomic Information for Mutual Defence Purposes with Britain, which was signed on 15 June 1955. A colonel and two majors from the USAF and the Armed Forces Special Weapons Project were given briefings on RAF aircraft to determine which US bombs could be carried. The Americans then wanted to know how many bombs would be required. The Minister of Defence, Harold Macmillan, determined that the V-bomber force would reach a strength of 240 aircraft during 1958. Each would carry one atomic bomb.
Dickson visited the US for talks with Twining in September 1955. A public announcement was made in the form of a news leak published in The Daily Telegraph and The New York Times on 8 June 1956, which was officially denied the following day. Agreement on the provision of American bombs—now called Project E—was reached, resulting in a detailed plan on 12 December 1956. This was then approved by the United States Secretary of Defense, Charles E. Wilson, and the Joint Chiefs of Staff. The UK government notified Wilson of its approval on 30 January 1957. The agreement was confirmed by Eisenhower and Macmillan, now Prime Minister, during their March 1957 meeting in Bermuda to repair the damage done to Anglo-American relations by the Suez Crisis. A formal Memorandum of Understanding was negotiated in Washington by the deputy chief of the Air Staff, Air Marshal Sir Geoffrey Tuttle, on 21 May 1957.
In a letter to Macmillan on 25 March 1957, Eisenhower stated:
Implementation Tactical bombers
It fell to the commander of the UK-based US Third Air Force, Major General Roscoe C. Wilson, to initiate Project E. Wilson had been liaison officer with the Manhattan Project, and Deputy Chief of the Armed Forces Special Weapons Project, and was very familiar with nuclear weapons. The first aircraft to be fitted for American atomic bombs were not V-bombers but 28 Canberra bombers earmarked as night interdictors for the Supreme Allied Commander Europe (SACEUR) in 1957. These were new B(I)8 models, which came straight from the manufacturer for modification to carry the Mark 7 nuclear bomb. The intention was that they would be able to carry either American or British bombs, but since the latter were not available, they were only fitted for American bombs. Later-model Canberras would be able to carry both. Since the specifications for the bomb bay doors said they opened wide, and the tail fins of the bombs were between wide, no problem was anticipated, but it turned out that the doors only opened between , depending on the aircraft, which meant that the bombs would have to be individually matched with aircraft. After some thought, was cut off each bomb fin.