The History of the Atomic Bombs

I wonder how much the Americans knew what they really had before they actually dropped that first one and then they realized how big a thing it was. The fact that the US waited three days to drop the second bomb was pretty much in keeping with the prediction made by General Leslie Groves who oversaw the entire nuclear program, the Manhattan Project. He had predicted early in the program that if the US had to drop atom bombs on Japan, of course, after Germany surrendered, and the entire Manhattan Project was predicated on a German bomb, which did not develop. So you see a timeline for the period between the first and the second bomb, very much in keep with what the US authorities had expected.