What about the naval base, the naval construction yard, the military headquarters and all the war material factories? Hiroshima and Nagasaki were just as much military targets as London, Birmingham, Liverpool, Dresden, Berlin, Hamburg, Munich, and much more so than Warsaw, Shanghai, Hong Kong, Rangoon, Mandalay, Antwerp, Brussels, Amsterdam, Rotterdam and Southhampton. There wasn't a major city in China, Burma, Malaysia, the UK, France, the Netherlands or Belgium that wasn't bombed by the Axis. The attitude on both sides of the war was that civilians built the sinews of the war machine, so they were valid military targets. Both the Luftwaffe and RAF had official positions that "dehousing" civilian workers was a laudable objective and not against the rules of warfare.