Was the extensive bombing of Germany in World War 2 nessesary?

Dresden, Hamburg, Berlin, Cologne etc, they where annihilated! Almost every city in Germany was destroyed, as in leveled. I know the Germans did a lot too in particular to Warsaw and St Petersburg, but it was nothing on the scale of what the allies did to Germany, The Germans in their bombing for the most part targeted factories, rail lines etc, but the allies targeted residential areas in Germany, was that necessary?