If Truman refused to use the atomic bomb on Japan, what should he have done instead?

[hunter]

60. They knew the Uranium bomb would work.

The danger of that design was the number of ways it might explode by accident. That's one reason they only made five of them. The other reason was that plutonium was easier to make by the ton than highly enriched uranium.

Plutonium isn't usable in a gun type bomb, the nuclear reaction tears a gun type bomb apart before it really has a chance to get going.

It was the detonators and electronics that were tricky in the implosion type plutonium bomb. This technology was one of the great atomic "secrets." The Trinity test fully demonstrated that they'd got it right. But even that wasn't much of an unknown. The uncertainty of the bombs working is another part of the myth. The reality is they knew the bombs would work.

What was unknown was the effect of nuclear weapons on cities. After Japan surrendered Hiroshima and Nagasaki were flooded with photographers, scientists, and technicians to study and document the damage done in minute detail. Nagasaki was a battlefield test of a "Fat Man" style bomb. 120 of those were made, all retired by 1950 as better, more efficient implosion bombs were built.