At the start of the Second World War in 1939, Bomber Command faced problems. The first was lack of size; Bomber Command was not large enough effectively to operate as an independent strategic force. The second was rules of engagement; at the start of the war, the targets allocated to Bomber Command were not wide enough in scope.

The Stirling was designed by Short Brothers to meet a Air Ministry specification from 1936. It entered service in early 1941 but had a relatively brief operational career as a bomber, being relegated to second line duties from late 1943, when other more capable four-engined RAF bombers, specifically the Handley Page Halifax and Avro Lancaster, took over the strategic bombing of Germany.

The Vickers Wellington was a British twin-engined, long range medium bomber designed in the mid-1930s. A twin-engined day bomber of perceptibly higher performance than any previous designs. It was widely used as a night bomber in the early years of the Second World War, before being displaced as a bomber by the larger four-engined "heavies" such as the Avro Lancaster. The Wellington continued to serve throughout the war in other duties, particularly as an anti-submarine aircraft.

The Handley Page Halifax was one of the four-engined heavy bombers of the Royal Air Force during the Second World War. A contemporary of the famous Avro Lancaster, the Halifax remained in service until the end of the war, performing a variety of duties in addition to bombing. The Halifax was also operated by squadrons of the Royal Canadian Air Force, Royal Australian Air Force, Free French Air Force, and Polish forces.

The Avro Lancaster is a British four-engined Second World War heavy bomber designed and built by Avro for the Royal Air Force (RAF). It first saw active service with RAF Bomber Command in 1942 and, as the strategic bombing offensive over Europe gathered momentum, it became the main heavy bomber used by the RAF, the RCAF, and squadrons from other Commonwealth and European countries serving within the RAF, overshadowing its close contemporaries the Handley Page Halifax and Short Stirling.The "Lanc", as it was affectionately known, thus became one of the more famous and most successful of the Second World War night bombers, "delivering 608,612 long tons of bombs in 156,000 sorties."