We had a total of three nukes, all different designs. The first one we set off to test. Until we did, we had no idea whether or not any would work. The next two we dropped on Japan. We dropped the second nuke on Japan a week after the first because they refused to surrender after we dropped the first one.
Imagine how history would be different if any one of the three nukes had failed to go off.
Exactly why Truman brushed aside suggestions that we “demonstrate” a bomb to the Japanese. You would waste one in any case; it might be a dud; and the impact either way was not guaranteed. Even if it worked, the Japanese might have said, “Big deal. It was a trick. You can’t do it over Japan.”
“We had a total of three nukes, all different designs. The first one we set off to test. Until we did, we had no idea whether or not any would work. The next two we dropped on Japan. We dropped the second nuke on Japan a week after the first because they refused to surrender after we dropped the first one.”
Trinity (16 July) was an implosion bomb as was the Nagasaki bomb (9 Aug). The Hiroshima bomb (6 Aug) was a gun-type bomb. There was very little doubt that the gun-type bomb would go boom. Therefore, there was no need to test that type prior to it’s operational use. The implosion bombs were much more complicated and there was enough doubt that they would work that we decided it was necessary to test an implosion bomb at Trinity before it was operationally deployed at Nagasaki.