Hiroshima and Nagasaki were the first places in the world, where the atomic bombs had been dropped. I wonder, if they did experiments with them. I think the cruel results have turned out to be a good lesson for the world not to use any A-bombs as weapons.
In this sense, I suppose, people in Hiroshima and Nagasaki made the supreme sacrifice, but in another they taught a significant lesson to human beings. Since then no other nations could use any more nuclear weapons.
I think it's not simply because once a country uses an A-bomb, others also will do; but because if it had been used against humanity, the nation could be condemned by the whole world, for nuclear weapons shouldn't be used against human beings.
I consider that the experiences in Hiroshima and Nagasaki have been the most effective deterrent.