Re: Just the Allies?
Guess the Axis powers' bombs weren't powerful enough?
The Luftwaffe had significantly less bombers than the RAF had, and they also had less capacity: their one heavy bomber was the Heinkel 177, 10 ton bomb load, mostly used on the Eastern front and only from by and large 1943. 1170 built (including prototypes and small-run specials). The Heinkel 111, Junker 88 and the Dornier Do 17 were used in the Blitz, were built in larger numbers (5500 Heinkels, 15000 Junkers, 2000 Dorniers), but those had a much smaller bomb load, only up to some 3000kg. Blitz raids were also quite spread out over time; they didn't make for concentrated ionosphere disruptions the way the raids over Germany did.
By contrast, at the start of the Area Bombing Directive early 1942 the RAF had the Halifax, Stirling and Lancaster, able to carry well over 5000kg (Lancasters had to be adapted to accept the Grand Slam), the lighter Hampden, Wellington, Whitley and the Mosquito, plus what the USAAF brought to the table once they came in. RAF Bomber Command was able to mount a number of "1000 bomber raids" with, in one case, 2000 tons of bombs dropped.