Between 1948 and 1992, personnel and aircraft of the United States Air Force (USAF) Strategic Air Command (SAC) were routinely deployed to bases in England. An informal agreement to base SAC bombers in the UK was reached between US General Carl Spaatz, and Marshal of the Royal Air Force (RAF) Lord Tedder, in July 1946. At that time there were only three bases in the UK deemed suitable for operating Boeing B-29 Superfortresses: RAF Lakenheath, RAF Marham and RAF Sculthorpe. These were airbases that had been extended during World War II when there were plans to use B-29s against Germany. When the Berlin Blockade began in June 1948, two B-29 groups deployed to the UK, but neither was equipped with Silverplate bombers capable of carrying nuclear weapons. Nuclear-capable Boeing B-50 Superfortress bombers began deploying in 1949, and nuclear bombs followed in 1950.

The original bases in East Anglia were considered inadequate for the deployment of the forces called for in the Offtackle war plan, and there were concerns that they were exposed to a surprise attack from the North Sea. New bases were developed at RAF Brize Norton, RAF Upper Heyford, RAF Fairford and RAF Greenham Common were therefore developed as bases, which began to be used in 1952. The bases were initially manned by the RAF, were handed over to the USAF in 1951. They continued to be known as RAF stations, and the Royal Air Force Ensign was flown alongside the flag of the United States. The B-29 groups on the UK and the depot at RAF Burtonwood were placed under the 3rd Air Division. It became the Third Air Force in 1951, and SAC activated the 7th Air Division to control SAC forces in the UK.

In 1953 the propeller-driven B-29s and B-50s were replaced with Boeing B-47 Stratojet deployments to English bases. These temporary duty postings (TDY) typically involved an entire wing of 45 B-47s, along with 20 Boeing KC-97 Stratofreighter aerial refuelling tankers, which were held at readiness at an English base for ninety days. In 1958 TDY postings were replaced by a new system of overseas deployments called Operation Reflex. A permanent SAC presence was established, with a SAC airbase group permanently assigned to each base, and the ninety-day deployments were replaced by twenty-one day deployments of two or three aircraft and crews. These aircraft were kept on full alert status for two weeks, which meant bombers and tankers were on the runway, fuelled and armed with a Mark 39 nuclear bomb, and ready to take off at 15 minutes notice. SAC B-47s in the UK were on alert during the Berlin Crisis of 1961 and the Cuban Missile Crisis, as were Thor missiles manned by RAF units, but with the warheads in the custody of SAC officers who controlled their launch through a dual key system.

With the introduction of intercontinental ballistic missiles and long-range Boeing B-52 Stratofortress bombers, SAC no longer required bases in the UK, and Reflex deployments ceased in 1965, but SAC bombers continued to visit, and the UK was used by the Lockheed U-2 and Lockheed SR-71 Blackbird reconnaissance aircraft. SAC Boeing KC-135 Stratotanker and McDonnell Douglas KC-10 Extender tankers based in the UK supported the abortive 1980 hostage rescue attempt in Iran and the 1986 United States bombing of Libya, and in 1991 joined B-52 bombers temporarily based in the UK to conduct bombing in Operation Desert Storm in 1991.

Early Cold War tensions During World War II, United States Army Air Forces (USAAF) personnel were deployed to the United Kingdom in large numbers, reaching a peak of over 400,000 in June 1944. Thereafter, numbers declined to 234,000 in April 1945 as personnel were deployed to the continent. Demobilisation was swift after the war, and by 1947 there were no US bases in the UK, and no numbered air forces deployed in Europe. Nonetheless, the war swept away traditional American isolationism. Wartime plans called for a worldwide network of 90 bases, but were cut back in 1944 when it was realised that the resources to support them would be lacking. These were intended to contain Germany and Japan, and enforce the peace settlement, not for a war with the Soviet Union. As early as May 1944, the Joint Chiefs of Staff had calculated that the war would leave the Soviet Union as a leading global power, and an assessment of its post-war capabilities was made in October 1945. It was not expected that the Soviet Union would resort to war with the United States, but war plans were drawn up for the possibility that such a war might occur as a result of a miscalculation.

Cold War tensions between the United States and the Soviet Union began as early as 1946. In June and July, the chief of the USAAF, General Carl Spaatz, met with the chief of the Air Staff (CAS), Marshal of the Royal Air Force Lord Tedder. The two were wartime comrades and had a warm personal relationship, and held each other in high regard. US war plans for a conflict with the Soviet Union assumed that Western Europe would be overrun, and a fighting withdrawal conducted to the Pyrenees. Strategic air operations would be carried out from the UK. Spaatz was interested in acquiring base facilities in the UK for B-29 Superfortress bombers armed with atomic bombs. Tedder, an enthusiastic supporter of close ties between the two countries, agreed to provide them. Spaatz briefed President Harry S. Truman on his return, and the prime minister of the United Kingdom, Clement Attlee, may have been informed of this informal agreement, but the Foreign Office and State Department were not.

In August 1946, Colonel Elmer E. Kirkpatrick, who had developed the base facilities on Tinian used for the atomic bombing of Hiroshima and Nagasaki, arrived in the UK to discuss the requirements. The B-29 was a large and underpowered aircraft. It needed a runway at least wide and long, with at least of clearance at both ends, and strong enough to bear the load of a aircraft with a Fat Man atomic bomb in the forward bomb bay, which required a concrete slab at least thick. The Fat Man also required special storage facilities and assembly workshops, as the bombs could only be assembled shortly before a mission. This required a specialised Armed Forces Special Weapons Project (AFSWP) team to be deployed from Sandia Base. Since there was insufficient clearance for a Fat Man under a B-29, loading was accomplished by driving the B-29 over a pit.

In 1946, there were three bases in the UK that met these requirements: RAF Lakenheath, RAF Marham and RAF Sculthorpe, which had been extended to a width of and length of when there were still plans to use B-29s against Germany. Early plans to deploy 24 groups of B-29 and Consolidated B-32 Dominator bombers in the UK were abandoned by 1944, and no B-29 operations were conducted from the UK during the war, although a lone YB-29, Hobo Queen (41-36963) was deployed to the UK on 6 March 1944. It tested US and British airbases for suitability for the B-29, and was shown off to distinguished visitors, including Tedder and Spaatz, before continuing on to India on 1 April. After the war three B-29s were stationed at RAF Mildenhall from March to October 1946 as part of Project Ruby, an evaluation of whether the B-29 could be modified to use the British Tallboy and Grand Slam bombs.

A survey of 105 airfields in the UK found another 23 suitable to be extended for use with the B-29. A meeting chaired by Air Vice-Marshal John Whitworth-Jones was held at the Air Ministry on 26 August to discuss the required works. In attendance was Sir Ernest Holloway, the Air Ministry's director general of works, who had directed the construction of airfields for the USAAF during the war. Works at Lakenheath and Sculthorpe involved the construction of pits near the hardstands, and the erection of additional buildings. The work was costed at £12,350 for each base, and were authorised on Holloway's personal authority. Hydraulic lift equipment for the loading pits arrived from Kirtland Army Air Field in September.

Two incidents in August 1946, in which one USAAF C-47 transport aircraft was forced down over Yugoslavia, and another was shot down ten days later, prompted Truman to order the Strategic Air Command (SAC) to stage a show of force as a warning to the Soviet Union to keep its client states under control. In November, six B-29s bombers from SAC's 43rd Bombardment Group were deployed to Rhein-Main Air Base in Germany, and for nearly two weeks they flew along the borders of Soviet-occupied territories and paid visits to bases of friendly countries, including the UK, thereby evaluating their suitability for future use. None of them were Silverplate bombers capable of carrying nuclear weapons; the US had only 17 of these at the time, all of which were assigned to the 509th Bombardment Group at Roswell Army Airfield in New Mexico.

The US National Security Act of 1947 established the United States Air Force (USAF) as an independent service, and SAC, which was formed as part of the USAAF in March 1946, was transferred to the USAF when the latter was formed in September 1947. SAC B-29s began deploying squadrons to Europe on a regular basis in 1947, and during that year, ten aircraft of the 340th Bombardment Squadron, 97th Bombardment Group deployed from Smoky Hill Air Force Base to Giebelstadt Army Airfield in Germany, for a thirty-day training/goodwill tour. Nine of them visited RAF Marham in a goodwill visit, where they were greeted by Lord Tedder and Major General Clayton Bissell, the US air attaché in the UK. Three of the bombers had been modified to carry Tallboys, which entered US service as the M-121. This revealed that despite the work carried out thus far, the air bases in the UK were ill-prepared to conduct B-29 operations.

B-29 deployments

Berlin Blockade When the Berlin Blockade began in June 1948, one B-29 squadron, the 353d Bombardment Squadron from the 301st Bombardment Group, was temporarily stationed at Fürstenfeldbruck Air Base in Germany. The group's other two squadrons deployed to Germany in July. The foreign secretary, Ernest Bevin asked Truman to send bombers to the UK to beef up the defences. In response, the 28th Bombardment Group from Rapid City Air Force Base in South Dakota deployed to RAF Scampton in Lincolnshire, and the 307th Bombardment Group from MacDill Air Force Base in Florida deployed to RAF Marham and RAF Waddington in Lincolnshire. Each group had three squadrons of ten B-29s. The first B-29 touched down on 17 July, piloted by Colonel John B. Henry Jr., the commander of the 28th Bombardment Group, who was greeted by Air Vice-Marshal Charles Guest, the Air Officer Commanding No. 1 Group RAF. The RAF granted permission, on the usual informal basis, for the USAF to reopen the wartime USAAF depot at RAF Burtonwood, and soon 2,500 USAF personnel were stationed there.

The presence of B-29s in the prompted members of the House of Commons, notably John Platts-Mills, to ask the Secretary of State for Air, Sir Arthur Henderson to press for details regarding the nature and duration of their deployment. Henderson replied in a written statement that the two groups were in the UK on temporary duty, and noted that "Units of the USAF do not visit this country under a formal treaty but under informal and long-standing arrangements between USAF and RAF for visits of goodwill and training purposes." Neither of the two groups deployed to the UK, nor the 301st Bombardment Group in Germany, was equipped with the Silverplate/Saddletree B-29s capable of carrying atomic bombs. Nor was the 2nd Bombardment Group, which arrived in August. Some confusion was caused by the arrival of "Colonel Tibbets", but this was Colonel Kingston E. Tibbets, the SAC deputy chief of staff for Materiel, and not Colonel Paul W. Tibbets of Hiroshima fame.