The "Luftwaffe" did not remain on the defensive in 1941 and 1942. Sperrle's air fleet carried out intensive and consistent air attacks on Britain and the limited German bomber force was reinforced over the winter, 1941–42. Concurrently, Sperrle with support from Hans-Jurgen Stumpff, continued to carry out air attacks on shipping. The Baedeker Blitz became the largest air offensive against Britain in 1942. The campaign was prompted by the bombing of Lübeck. Hitler ordered Sperrle to bomb British cities that held cultural significance. Hitler specifically outlined the terrorist purpose of the bombing offensive aimed at civilian centres for the greatest impact on the British populace. The blitz was accompanied by fighter-bomber attacks against London and coastal towns, which took place until June 1943. In April 1943, Sperrle's air fleet could still muster 120 aircraft for these operations. The purpose of these fighter-bomber ("Jabo") operations, which began from autumn, 1942, was for "reprisals", similar to the German bomber campaign.