Was the atomic bombing of Hiroshima and Nagasaki necessary?

On August 6 and 9 1945, atomic bombs were dropped and destroyed the Japanese cities of Hiroshima and Nagasaki.

The bombings led to the Japanese surrender and the end of World War II.

Was the dropping of the first bomb necessary and did a second have to be dropped?

Did the awesome devastation of Hiroshima and Nagasaki inadvertently create a stand-off between the super powers that lasted for 45 years or would a stand-off have resulted anyway just knowing their destructive power?

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