I thought FirstClassSkeptic's comment was so good I copied it, above. (It is from a discussion on whether radiation was propaganda, or not). Here's my George Bernard Shaw-style attempt to dramatise part of what might have happened. Some of the dialogue is a bit stereotypical.
Secret meeting in Los Alamos April 1945. Cigar smoke and the smell of brandy fill the air of the hot desert evening.
GROVES: Well, gentlemen, let's get to work. Let's review the situation.
SACHS: Oy vey, the Germans are still holding out. Think of the money we are losing not printing Deutschemarks.
GROVES: Say, the Fed ain't everything, you know
SPAATZ: We are bombing Germany all the time now. And strafing. It sure is fun to bomb and shoot them Germans. But [sigh] what we need is really big bombs. Them blockbusters just ain't big enough. We drop whole blizzards of them bombs, but it's a slow job, we need loadsa planes. [Sigh]. [Brightens up:] Firebombs are great for gooks, though.
SACHS: Oy vey, just don't bomb Ford Motors - we put a lot of money in dem factories!
OPPENHEIMER: Spatz, you want a big bomb. This is where we can help. This is why you're here. Me and GG, General Groves, that is. We've been working for years on nuclear weapons. Secret project. You heard of ee equals em cee squared?
SPAATZ: Don't call me spats. It's Spaatz, Spaarrrtz. But sure, I heard a that Einstein baloney.
OPPENHEIMER: This is of course top secret. GG will fill you in.
GROVES: Oppy here and the long-hairs have made great progress. The bomb is almost ready. Well, it's been almost ready for years now. [Laughs]. But we're ready to test. Just in time, eh Oppy? [Winks at Oppenheimer]
SPAATZ: Suppose it don't work?
GROVES: We thought a that. We'll try it on Japan. Or we'll pretend. Nobody can understand Japanese anyway! Besides we can control their news.
SPAATZ: Waal, OK, just make sure it ain't too heavy. Say - just how big a bang will these things do?
OPPENHEIMER: Spaatz, the sky's the limit. We may blow up the whole world! There's no limit! It's real great! Well, that's in theory. We invented this word, kilotons, that's of TNT. Thousands of tons. Huge blast and we got writers working on the descriptions - we quite like 'mushroom cloud of deadly poison radiation'. Lemme quote the Bhagavad Gita...
SPAATZ: Never mind that, Oppenheimer. Say I hear there's trouble starting in India - trust them Brits to bugger it up. But anyway - a real big bomb? We'll rule the world! One plane will make 'em cower down! The US will rule everyone! It's just great! I run the airforce - I'll be dictator!! We'll rule Europe. And all a south America. Maybe we'll get them Africans working! And we can tell Stalin where to shove it [swigs brandy]
SACHS: Oy vey, Stalin is our brave ally, and vot an investment manager he is
SPAATZ: Could be a little problem. Them B29s go real fast, they claim 400 miles an hour. That's 600 feet a second. All it needs is some bomb-aimer jerking himself off to some comic, and you overshoot a coupla miles. We're trying to automate it. But then they keep finding noo winds, strong winds. And the characteristic way the things fall makes a helluva difference. So it ain't that easy hitting a target. A few miles...
GROVES: Umm well. Lemme tell ya something, Spaatz. I'll be honest with you. I'm gonna be honest. But lemme tell ya this. If news of our little meeting gets out, you get trouble. You get the sack. Understand? No more work, see? And it's wartime and things might just happen to you, savvy?
SPAATZ: Sure, GG
GROVES: We ain't 100% sure this thing will work. I'm being honest. It hasn't been tested. Who knows. Now Oppy and his long-hairs say they are sound people, but I'll be honest with you - I don't always understand what they do. And half the time they're gabbling with Stalin's group. Sometimes even them Germans. Oppy says the chance of success is 50%. But he goes a bit quiet when I ask questions. They all go quiet. So he would say that. Anyways we have a test rigged up in the desert - plus a duplicate with a pile of TNT to impress people just in case it don't work.
SACHS: They sure have used a lot of money on this project. But there's plenty more in the Fed. You want money - we gottit!
GROVES: Sure you have. And I'm real grateful. Now, we're going to test at night so nobody can really see what's going on.
OPPENHEIMER: GG, I do have some papers and stuff hidden away, just in case something happens to me. But gentlemen, gentlemen, let me remind you - this war is nearing the end. It's bin good for all of us. But we have to think what we'll do after. After the first war, there sure were a lot of pensioned-off brass!
SPAATZ: If we get these big bombs, then we can bomb anyone we want. I'll be in work forever. Not sure about Groves, though! Or Oppenheimer! Once it's invented, that's it. We won't need you. Still, you have your family clothes business. [laughs]
GROVES: Spaatz, you haven't understood. If it works, we make plans. We have Franck working on some dumb report for Stimson. We leak it, so people get worried. But we have to make a plan when - err if - it don't work. But see we have big enough bombs now to pretend, if we have to. And them aiming isn't a problem. There's this great stuff called napalm, sort of jelly, makes a big cloud a smoke, better than these cylinder bomb things. We got better explosives now. We have aluminum powder.
SPAAZT: You can't be serious! People will find out
GROVES: That's what I thought. But there's this great new invention, tele-vision they call it. Like a little cinema in your own house. Damned if I can figure out how they get the little men in there. But Sachs knows all the brass at Radio City and NBC and the rest, and they will say whatever's needed.
SPAATZ: [Thoughtfully] Well, it's true there was a firestorm at Dresden and a good one at Tokyo, too. Whole place burnt up, bodies turned to hot dust. Who would know what caused it? We have the whole journalism corps and none of them ever step outa line. Anyway, why would any country take the risk if we threaten them? Didn't we win the biggest war in history? Besides, I don't wanta join unemployment lines after the war! I might end up in journalism for chrissake. Say, what does Eisenhower say? Roosevelt?
GROVES: Eisenhower is only interested in killing them Germans before Yo Kipper, whatever they call it. He's on a roll. Then when we win he's got years of fun ahead of him. There's this plan to make all Germany rural, bit like the dustbowls, some guy called Morgen something thought it up. But Roosevelt might be difficult. I know he's lied about his wheelchair all this time. But he might not go along with this.
SACHS: Well, we have plans for that. The Special Services...
GROVES: [Interrupts] I think you can be sure it'll go smoothly.
OPPENHEIMER: What if someone else says they know how to do it? Could be a problem. There are scientists all over the world. If we bluff, what's to stop them doing the same? Of course, we are mostly friends, there is that. Professional solidarity, you might call it.
GROVES: Well, there's a lot of scope for deception here. Radiation, that's real dangerous. It might spread all over. And we got big blasts. Giant blasts. Directed blasts. Air blasts. Noo bombs using noo ideas. Noo delivery systems. Noo dangers. Noo elements. Big bombs, small ones. Air ones. Ground ones. Underground ones. Smuggled ones. The public won't know they're coming or going.
OPPENHEIMER: We could plan a few leaks and a few spies with a lotta publicity. Then we could tighten up security! No passports, that kinda thing. No access to plant. Complete secrecy. Military police. Keep them in the dark! So we'll all be in work! Sounds great.
SACHS: And my people can get to Israel. If they want to or not. We have to do something about the British though.
GROVES: One a them limeys called me a gullible builder! Can you believe that. [Bites cigar angrily]. A few hanged officers would do it. Hey, do you have any legal rights?
SACHS: We'll rig up some phoney trial with our politbureau science mates and Stalin, to get the sheep on our side. Kill off der German leaders - give the bastards what they deserve. Torture them. Get them all outa the way. It'll take a few years - 1948 should be about right. Time to fix up the details with Stalin. Palestine - who cares about legal rights already? Democracy shamocracy.
GROVES: Right. OK. Look. Here's my plan. We gotta have bombs for Japan. So we ship a coupla dummy bombs to Tinian. With a film crew. Tricky because the sailors mustn't know it's phoney. They have to look good. Stick some aerials on them. Make them look heavy. Any leak, we have to take serious action. Has to be done soon. Then after that we run the test and order the press to come. We'll call it 'Trinity' to give em a thrill. Film it from a few miles and tell them what to print. Newsreels and radio too. But full wartime censorship. We check everything.
SPAATZ: Now, Japan is trying to surrender so we haven't got too much time. We're holding them off. After we'll brief the press for maybe twenty years after the war. The new world begins, with the USA as the dictator of the world!
SACHS: Zere are some opportunities in Japan!
SPAATZ: Word from LeMay is the Japs had a takeover. This Bushido crap is dead. If we flatten the cities, they can build after the war, with no land ownership problems - skyscrapers and bathrooms and all that. Sort of free-of-charge land clearance scheme from us, courtesy of Uncle Sam.
SACHS: Sounds good, already. And cheap labour after the war. These white guys ain't no good at work, but we won't tell 'em. [Laughs]
SPAATZ: What about Churchill?
GROVES: Churchill knows nothing. Anyway his advisor is another one of the chosen. Stalin knows nothing. Mustn't push Stalin though. If the thing doesn't work, we can't risk him fighting on. He wouldn't care if a few millions Russians died. So we concede. Eastern Europe's a shithole anyway. All agreed?