So what if there was a lot more strategic bombing of Germany during World War II?
Instead of building an invasion force for D-Day and hitting German industry, what if the Allies decided the best they could would be to simply wipe out German cities one after the other. This would mean huge bomber raids, day and night over short periods of time by the RAF and the USAAF, all aimed at annihilating as many cities as possible. Due to the high raid intensity over certain targets (principally an almost 24 hour bombing over 3-4 days) the cities are totally ruined, recover efforts fail, civilians sufficate in the bomb shelters, more firestorms are started.
Raids would be focused on Northern and Central Germany, not go too far to the South in order to avoid exposure to german fighters.
It's a gamble, but can the Allies break German morale so far, so that a counter coup is staged, Hitler gets killed and the Germans sue for peace in the West in order to turn their attention to the Soviet Union?