It is a tricky one. I agree with most of what's already been said and, would add, that the bomb had not been properly 'tested' and so a lot of the devastation and subsequent effects of the radiation only became apparent after the event. It may have been that the allies wanted this to happen, but I bet even they didn't anticipate how bad it would be.If you've ever watched the World at War series, which is just excellent (and distressing in equal measure), you will have seen the section on the war against Japan, where American casualties were running at 50% fighting for each tiny island, dealing with an enemy who fought to the death. Faced with this, or dropping a big funkin' bomb and stopping them in their tracks, appeared to be a 'no-brainer' under the circumstances.For me, the bombings were awful, but necessary to prevent an excessive escalation of the war. The rape of Nanking had advertised the brutality of the Japanese in conflict against civilians, so the British and Americans had absolutely no hope of mercy:http://www.historyplace.com/worldhistory/genocide/nanking.htm
In case you can't be bothered reading this, here's a lovely excerpt:'In December of 1937, the Japanese Imperial Army marched into China's capital city of Nanking and proceeded to murder 300,000 out of 600,000 civilians and soldiers in the city. The six weeks of carnage would become known as the Rape of Nanking and represented the single worst atrocity during the World War II era in either the European or Pacific theaters of war.The actual military invasion of Nanking was preceded by a tough battle at Shanghai that began in the summer of 1937. Chinese forces there put up surprisingly stiff resistance against the Japanese Army which had expected an easy victory in China. The Japanese had even bragged they would conquer all of China in just three months. The stubborn resistance by the Chinese troops upset that timetable, with the battle dragging on through the summer into late fall. This infuriated the Japanese and whetted their appetite for the revenge that was to follow at Nanking.After finally defeating the Chinese at Shanghai in November, 50,000 Japanese soldiers then marched on toward Nanking. Unlike the troops at Shanghai, Chinese soldiers at Nanking were poorly led and loosely organized. Although they greatly outnumbered the Japanese and had plenty of ammunition, they withered under the ferocity of the Japanese attack, then engaged in a chaotic retreat. After just four days of fighting, Japanese troops smashed into the city on December 13, 1937, with orders issued to "kill all captives."Their first concern was to eliminate any threat from the 90,000 Chinese soldiers who surrendered. To the Japanese, surrender was an unthinkable act of cowardice and the ultimate violation of the rigid code of military honor drilled into them from childhood onward. Thus they looked upon Chinese POWs with utter contempt, viewing them as less than human, unworthy of life.The elimination of the Chinese POWs began after they were transported by trucks to remote locations on the outskirts of Nanking. As soon as they were assembled, the savagery began, with young Japanese soldiers encouraged by their superiors to inflict maximum pain and suffering upon individual POWs as a way of toughening themselves up for future battles, and also to eradicate any civilized notions of mercy. Filmed footage and still photographs taken by the Japanese themselves document the brutality. Smiling soldiers can be seen conducting bayonet practice on live prisoners, decapitating them and displaying severed heads as souvenirs, and proudly standing among mutilated corpses. Some of the Chinese POWs were simply mowed down by machine-gun fire while others were tied-up, soaked with gasoline and burned alive.After the destruction of the POWs, the soldiers turned their attention to the women of Nanking and an outright animalistic hunt ensued. Old women over the age of 70 as well as little girls under the age of 8 were dragged off to be sexually abused. More than 20,000 females (with some estimates as high as 80,000) were gang-raped by Japanese soldiers, then stabbed to death with bayonets or shot so they could never bear witness.Pregnant women were not spared. In several instances, they were raped, then had their bellies slit open and the fetuses torn out. Sometimes, after storming into a house and encountering a whole family, the Japanese forced Chinese men to rape their own daughters, sons to rape their mothers, and brothers their sisters, while the rest of the family was made to watch.Throughout the city of Nanking, random acts of murder occurred as soldiers frequently fired their rifles into panicked crowds of civilians, killing indiscriminately. Other soldiers killed shopkeepers, looted their stores, then set the buildings on fire after locking people of all ages inside. They took pleasure in the extraordinary suffering that ensued as the people desperately tried to escape the flames by climbing onto rooftops or leaping down onto the street.The incredible carnage - citywide burnings, stabbings, drownings, strangulations, rapes, thefts, and massive property destruction - continued unabated for about six weeks, from mid-December 1937 through the beginning of February 1938. Young or old, male or female, anyone could be shot on a whim by any Japanese soldier for any reason. Corpses could be seen everywhere throughout the city. The streets of Nanking were said to literally have run red with blood.Those who were not killed on the spot were taken to the outskirts of the city and forced to dig their own graves, large rectangular pits that would be filled with decapitated corpses resulting from killing contests the Japanese held among themselves. Other times, the Japanese forced the Chinese to bury each other alive in the dirt.'