[argumentum]

"It is widely considered a war crime"

Evidence? Whether allied strategic bombing of Germany/Japan was a "war crime" is partly a legal / technical question:

https://en.wikipedia.org/wiki/War_crime#Definition

In regard to the strategic bombing during World War II, it should be noticed that at the time, there was no international treaty or instrument protecting a civilian population specifically from attack by aircraft,[34] therefore the aerial attacks on civilians were not officially war crimes. Because of this, the Allies at the trials in Nuremberg and Tokyo never prosecuted the Germans, including Luftwaffe commander-in-chief Hermann Göring, for the bombing raids on Warsaw, Rotterdam, and British cities during the Blitz as well as the indiscriminate attacks on Allied cities with V-1 flying bombs and V-2 rockets nor the Japanese for the aerial attacks on crowded Chinese cities.[35]