Undoubtedly one of the major influences on World War II, and one of the greatest aircraft of history, the "Lanc" came about because of the failure of its predecessor. In September 1936 the Air Staff issued specification P.13/36 for a twin-engined bomber of exceptional size and capability to be powered by one of the very powerful engines then under development: the Rolls-Royce Vulture 24-cylinder X engine was preferred. Handley Page switched to four Merlins with the Halifax, but A. V. Roe adhered to the big-twin formula and the first Type 679 Manchester flew on 25th July 1939. Altogether 209 Manchesters were delivered by November 1941, but the type was plagued by the poor performance and unreliability of its engines. Though it equipped eight Bomber Command squadrons, and parts of two others plus a flight in Coastal Command, the Manchester was withdrawn fromservice in June 1942 and survivors were scrapped.
Nevertheless, the basic Manchester was clearly outstandingly good, and in 1940 the decision was taken to build a longer-span version with four Merlin engines. The first Lancaster (BT 308) flew as the Manchester III at the beginning of 1941. So outstanding was its performance that it went into immediate large-scale production, and Manchesters already on the line from L7527 onwards were completed as Lancasters (distinguished from later aircraft by their row of rectangular windows in the rear fuselage). Deliveries began early in 1942 to 44 Squadron at Waddington, and on 17th April 1942 a mixed force of 44 and 97 Squadrons made a rather foolhardy daylight raid against the MAN plant at Augsburg, whereupon the new bomber's existence was revealed.
From then until the end of World War II Lancasters made 156,000 sorties in Europe and dropped 608,612 long tons of bombs. Total production, including 430 in Canada by Victory Aircraft, was 7,377. Of these 3,425 were Mk I and 3,039 the Mk III with US Packard-built engines. A batch of 300 was built as Mk IIs with the more powerful Bristol Hercules radial, some with bulged bomb bays and a ventral turret. The Mk I (Special) was equipped to carry the 12,000 lb (5,443 kg) light-case bomb and the 12,000 lb and 22,000 lb (9,979 kg) Earthquake bombs, the HS radar blister under the rear fuselage being removed. The Mk I (FE) was equipped for Far East operations with Tiger Force. The aircraft of 617 (Dambusters) Squadron were equipped to spin and release the Wallis skipping drum bomb. The Mk VI had high-altitude Merlins and four-blade propellors and with turrets removed served 635 Squadron and 100 Group as a countermeasure and radar spoof carrier. Other marks served as photo-reconnaisance and maritime reconnaisance and air/sea rescue aircraft, the last leaving RAF front-line service in February 1954.
Lancasters took part in every major night attack on Germany. They soon showed their superiority by dropping 132 long tons of bombs for each aircraft lost, compared with 56 (later 86) for the Halifax and 41 for the Stirling. They carried a heavier load of bigger bombs than any other aircraft in the European theatre. The 12,000 lb AP bomb was used to sink the Tirpitz, and the 22,000 lb "Grand Slam" weapon finally shook down the stubborn viaduct at Bielefeld in March 1945. Around Caen, Lancasters were used en masse in the battlefield close-support role, and they finished the war dropping supplies to starving Europeans.