When were Americans made aware of the nuclear bombs droped in Japan?

According to this, and another source, they were informed about the first bomb no later than August 7, 1945.

Funnily enough, I’m reading a novel based on the experiences of the wives at Los Alamos. According to it, it was on the radio that day.

I suppose it would have been next to impossible to keep the instant vaporisation of 2 cities full of innocent civilians secret.
The real question is, how many American citizens felt any shame?

Far from being top secret the bombings were all over the news. The US couldn’t wait to crow about its new toy.

It was secret until made public the day of the drop. My MIL (now 90) worked in one of the labs that helped develop and understand the effects of the bomb. She did not tell anyone what she did.
One of her prize possessions is a 35 mm color slide taken of Trinity. It is stored in the safe.

@ragingloli I suppose it would have been next to impossible to keep the instant vaporisation of 2 cities full of innocent civilians secret.
I guess it is a good thing the US won or someone may have been facing war crimes, maybe not Patton, maybe not Ike, but surely some admirals, and others who fire bombed innocent people and maybe killed more…....holy smokes Bullwinkle, @ragingloli and I are in agreement on something, run, someone may get struck by lightning ~~

@LuckyGuy Yes, according to this book, even the wives who lived at Los Alamos didn’t know what their husbands – and some woman scientists – were working on.

There’s a terrific new TV series running called Manhattan about the Manhattan Project, the making of the bomb. I highly recommend your watching it. Googling will fetch you many, many sources on this project.

After the bombs were dropped. Japan conceded defeat immediately after the second, so no point in putting off the news any longer.

MIL kept the slide hidden (a secret treasure) at least until the late 1970’s! Incredible.
The amazing thing is that they figured it all out and built it without really understanding everything involved. On youtube you can find movies of the engineers setting up the test bomb and positioning it They are walking around with no shirts or hard hats. Some are wearing sunglasses. Basically they have no protective gear at all. The soldiers, technicians and engineers watching the blast were told to avert their eyes. There was no mention of radioactivity. Nobody had a clue.

@LuckyGuy Nobody had a clue.
That is why they fire and carpet bombed everyone else but left Nagasaki and Hiroshima untouched as to see the full effects of the bomb on a blank canvas, they were merely life human guinea pigs.

Oh they knew exactly what they were dealing with. Make no mistake.

You can find movies of the engineers setting up the test bomb and positioning it They are walking around with no shirts or hard hats.

The plutonium was shielded. They knew that. You know that, right?

This was War. Japan made a big mistake by hitting Pearl Harbor that Sunday morning. .
@Hypocrisy_Central They only carpet/firebombed targets that were easy to hit. The southern coastline was easy pickings. They hit industrial cities. Concentrating on Tokyo and Yokohama. They could have firebombed the whole island but they didn’t – at least at that point. If you are going to drop an experimental bomb would you drop it on a place you have already destroyed?
@jaytkay Of course it was shielded! Or as shielded as they thought was necessary. What they did not know was the level of damage small amounts can do. They were still screwing around with it in the 50’s. (Watch this cleansing cream commercial.)
@Darth_Algar They had done the math and knew the ideal. They did not know if they could really do it. They were not sure it wold actually light off.
They did not completely understand the health effects. If they did, they would not have subjected their own troops to the poison. They actually believed it would be safe to fire a nuclear mortar shell and have troops move it right after the blast.
Here’s my final proof of ignorance. Later tests allowed big shot politicians, big business executives, and military brass to enter the restricted areas and get a front row seat so they could watch the fireworks! They were handed dark glasses to protect their eyes. Dark Glasses! Ignorance…
Although, truth be told, I’d like to invite a few big shot politicians, big business executives, and military brass to stand near a nuke test now.

Here’s my final proof of ignorance. Later tests allowed big shot politicians, big business executives, and military brass to enter the restricted areas and get a front row seat so they could watch the fireworks!

The proof would be how many suffered from radiation-induced illness.

I knew a guy who as a young GI was ordered to watch a Nevada nuclear blast. He died 10 years ago from lung cancer after 60 years of smoking.

I’m not aware of widespread harmful radiation exposure in the US since the 1920s Radium Girls.

@LuckyGuy “They actually believed it would be safe to fire a nuclear mortar shell and have troops move it right after the blast.”

No, they did not actually believe that, hence why that weapon was never actually put into use.

“Here’s my final proof of ignorance. Later tests allowed big shot politicians, big business executives, and military brass to enter the restricted areas and get a front row seat so they could watch the fireworks! They were handed dark glasses to protect their eyes. Dark Glasses! Ignorance…”

And how many of these big shot politicians, business executives and military brass suffered blindness or eye damage because of this supposed ignorance?

It would have been impossible to keep that a secret as soon as the first drop happened, unlike the slaughter/genocide of millions of innocents the Germans were committing that was sly, systematic and well-hidden from the international community.

The real question is, how many German citizens felt any shame?

There was no justification for such a massive display of power as the destruction of Hiroshima and Nagasaki, causing the deaths of hundreds of thousands. It was a desperate move against the nation of an aggressor. As a war-ending strategy it was certainly effective.

World War II should always be held in our hearts as an example of how truly awful humans can be to each other.

@Darth_Algar “They actually believed it would be safe…” ” hence why the weapon was never actually put into use.” In the beginning they did. A few months after Hiroshima they started to figure it out. It took years for one group to convince the other group that it should not be made/used. In 1953 they were still building and testing the systems See Upshot-knothole Grable
(You can easily find other references now that you have the name.) The naive idiots outfitted troops with gas masks using particle filters! They thought it was the dust that did damage.

Re.: the big shots and how many became blind. I figure very few had eye damage. They protected their eyes with the magic glasses. It was their bodies that were unprotected. How many died early? According to some studies up to 11,000 Americans died. Reference and interesting photos of big shots and troops watching the blasts . We will never know how many died early from prostate cancer, hemophilia, colon cancer, etc. Cigarette smoking and other dangegot them first.
By 1960 they pretty much figured out that you do not want to be anywhere near a blast..

As an aside, I have access to a lens doped with thorium that was made in the early 60’s. They used thorium because it affected the index of refraction that improved the optical characteristics. Unfortunately it was extremely radioactive. Anyone who used it was exposed.
Also look up the history of the “girls” who painted the glow in the dark marks on the radium dial watches. They suffered from awful mouth cancers many years down the road.

Building/testing systems is not the same as putting those systems into battlefield use. Frankly with the advent of nuclear weapons it made a certain sense to build and test every conceivable method of deployment.

They may not have taken the best precautions to shield themselves from radioactive fallout, but they were not wholly ignorant of it’s effects.

I know all about the “girls”. I happen to live in “Radium City”. Not sure what the connection between them and nuclear weaponry is. Actually by bringing them up you kinda prove the case that the effects of radiation were already known by the time the atomic bombs were developed. The operators of the Radium Dial Company and the scientists employed by them were careful to avoid exposure to the radium while keeping the girls in the dark about its negative health effects. The company settled with the girls in the late 1920s, agreeing to pay their medical expenses for life.

I brought up the radium as an example that shows hows early people/users did not know. Heck, Madam Curie died of radiation poising. The big boys at the Radium dial company figured it out a few years later but did not stop the process that let many “girls” suffer the effects down the road.
They were not aware of the fallout danger immediately. They knew there might be something going on but did not have the data. They knew that very high numbers were dangerous but thought low number were ok. If the generals thought there was any chance of getting radiation poisoning they would not have sat right up front and center.
Frankly I’m surprised nobody in that picture was smoking a cigarette.

One more example of not having a clue was the “little” miscalculation of the Li 6 and Li 7 in the early H bomb. They thought Li 7 would be inert and would not add to the power of the bomb. Wrong. The bomb was about 2x what was expected. It blew apart the monitoring station.
Here is a video on it. The DOE has released a lot of info.

None of this has to do with the OP’s question: When did the public know? The answer remains: it was secret until the bomb went off in Japan.