Then Hap Arnold then, who deliberately firebombed Japanese cities trying for the largest amount of damage? And what factory was at ground zero at Nagasaki or Hiroshima?
That would be Curtis LeMay. Hap Arnold was Chief of the Army Air Forces. LeMay was the commander of the Army Air Force units in the theater. The decision was his, although it was later ratified by Arnold and the Joint Chiefs.
Nagasaki was the location of the Mitsubishi electrical works. That facility was as large and significant to the Japanese war effort as the Westinghouse East Pittsburgh Works or the General Electric Schenectady Works were to the US war effort.
Hiroshima was a major Japanese Army headquarters.
And throughout ever city in Japan, thousands of small "cottage" factories were established turning out arms and ammunition of all types.