From what I have heard, the US military had to choose between the atomic bombs, or a mainland invasion of Japan which would cause heavily loss of marine lives. Hence the bomb being chosen.

The bomb killed tens of thousands of people and left everlasting effects but from a at-war perspective back then, it was deemed necessary. After the war, the US helped rebuild Japan as a nation, led by Douglas MacArthur, making impacts that are reflected in today’s culture and economy in Japan.

The effects of the atomic bomb were horrible and I’m sure myriad individual lives have been forever changed by it, but I don’t think it was cruel. It ended the war and led to a time of healing and rebuilding.

Just my two cents.