It's true that there are very few examples in 20th century history of a bombing campaign that actually broke the morale of a people at war and sapped them of the will to continue the fight. The Battle of Britain did nothing but harden the resolve of the English, and the destruction of German cities didn't stop the German people from fighting on to the end (even if Bomber Harris and Hap Arnold did much to hasten that end). The use of nuclear weapons was effective in the Pacific, but only after horrific fire bombings that did nothing to bring the Japanese to heel. Bombing worked in Serbia, but not in the First Gulf War or Vietnam.