Completing today's trifecta of depressing posts, I may as well note that today marks the 67th anniversary of the dropping of the atom bomb on Hiroshima by American forces. A few days later, America would drop a second atom bomb on Nagasaki, as though to tell the Japanese that they would run out of cities long before we'd run out of bombs. Their emperor surrendered shortly after that, and the most destructive war in history finally came to a close.
The decision to use the atomic weapon is controversial today (though rather popular at the time among Americans. Among Japanese, I assume it wasn't popular at all). The main reasons for using this unconventional weapon boil down to:
1) Dropping the bomb killed a great number of mostly innocent civilians--several tens of thousands--however, this was the necessary shock effect to end the war. The alternative would have been an invasion of Japan, with casualty counts among American troops and Japanese civilians being far greater. Dropping the bomb, in a way, was more humane.
2) The hell with Japan because screw those guys. They started the war with us, and war is hell. They invited every bit of destruction we brought on them.
3) We had another reason for using the atomic weapons in this manner. Demonstrating to the world what the wartime use of these weapons would mean gave a strong signal to our future enemies, namely the Soviets. The sacrifice of tens of thousands of Japanese--who totally had it coming, see 2) above--had the result that for the 67 years since 1945, no two major powers would get into a full scale total war with one another. The knowledge that a weapon that could be dropped from a single plane (or later sent by a single rocket) and destroy an enemy city surely had something to do with this.
On the other hand, each of these reasons could be countered:
1) At that point in the war, Japan's navy was almost entirely at the bottom of the ocean, their air force was a hollow shell of what it used to be, and their ability to continue the war in any meaningful way was severely limited. (Islands can't pose much threat without planes or ships, and Japan lacked the natural resources to rebuild without imports of materials from abroad). If we did have to invade, the die-hard remnants of the Japanese Army on the home islands may have put up a suicidal last stand, but it would have fallen apart before any serious American casualties would have stacked up.
2) Japan may have started the war, but vengeance shouldn't be a war aim. And how far should retaliation go? Deliberately killing large numbers of civilians is beyond the norms of a civilized country. It's one of the things that separates us from our more craven enemies. We shouldn't be stooping to this sort of revenge.
3) If we really wanted to scare the Soviets we should have nuked Berlin after that city surrendered. Then they would have seen that (a) we could wipe out a city much closer to them and (b) we are just crazy enough to nuke a city in a country that is no longer at war.
I won't second-guess President Truman's decision to use the atomic bombs here--hindsight being 20/20 and all, plus the fact that even today the points above are still up for lively debate--and he had to make a tough decision with the best knowledge he had at the time. We can be glad though that despite the horrifying example of destroying those two cities, Japan became a peaceful economic power afterwards, and no country has ever used this sort of weapon again.