Atomic Weapons Before WW2

[Volyn]

Assume that the following nations (Nazi Germany, Imperial Japan, USSR and USA) possess less than a dozen usable atomic weapons, with a yield equivalent to the "Fat Man" bomb of 21 kt, prior to September 1939. Since an air deliverable A-bomb was not possible for any aircraft at the time, it would need to be a sea or land based weapon.

TOPIC: How would these nations use atomic weapons in the early years of the war, based on the same type of delivery platforms available for that era?

Could the IJN use a merchant ship to carry one of the bombs into Pearl Harbor and detonate it next to Battleship Row, or any other military/civilian target of convenience? Would the Japanese use an A-bomb on Singapore as well with 85,000 British soldiers in garrison? Maybe the Chinese National Army would have been destroyed on the battlefield with a few atomic blasts?

The Nazi government could send a diplomatic train to Moscow with a few atomic devices stowed aboard; the daisy-chained atomic blasts would ensure Moscow resembled Nagasaki or Hiroshima. Would the Germans nuke Warsaw, Paris or London?

How would the USSR have employed these weapons, would they be used on their own soil in an attempt to stop the German invasion or would the Red Army go on the offensive first and attempt to conquer Europe?

We know the USA used 2 weapons at the end of the war, when they were trying to force the Japanese to finally surrender. However, if they had the A-bomb sooner, would it be used on Tokyo at the earliest possible opportunity?

[OpanaPointer]

Merchant traffic not already cleared was not allowed into Pearl. They anchored off Honolulu.

BTW, the US had a third atomic bomb ready and General Marshall was to be give a total of ten bombs for use during the invasion of Japan. The NSA bomb docs (online) document that three bombs a month would have been the guaranteed output by November 1945.

[Volyn]

Merchant traffic not already cleared was not allowed into Pearl. They anchored off Honolulu.

What defenses would have stopped a "stray" merchant ship from encroaching into Pearl? And if they can't get in, then they can hit the next target of choice Honolulu.

BTW, the US had a third atomic bomb

Was it part of the original shipment to Tininan? Either way I have corrected my prior statement, thanks for the heads up.

[OpanaPointer]

There were warships patrolling the entrance. Famously, USS Ward was on that duty on the morning of Dec. 7th. She attacked a midget sub and then escorted a stray fishing boat to Honolulu, where she turned the boat over the Coast Guard who had the duty of yelling at interlopers. Ships that had no business being at Pearl were pounced on if they got too close to the entrance. Now, depending on the size of the bomb a stand-off attack could have done some damage, but the optimum height for the US atomic bombs was ~1870. The slightly elevated terrain of the Hickam airfield would have deflected some of blast.

[Takao]

Huh?

The US had the XB-15 in 1937, and the XB-19 in 1941, both would have been capable of carrying Little Boy.

[Volyn]

The US had the XB-15 in 1937, and the XB-19 in 1941, both would have been capable of carrying Little Boy.

The XB-15 were not built in any numbers, and the XB-19 did not make its maiden flight until 27 JUN 1941. So they were not available for use, by the time the war began on 1 SEP 1939.

[Carl Schwamberger]

BTW, the US had a third atomic bomb

Was it part of the original shipment to Tininan? ...

The Plutonium core was enroute. Approximately a dozen implosion devices were already there, without Pu. cores. Another Pu. core was near completion, that is the shaping of the multiple slugs with machine tools.

[T. A. Gardner]

Assume that the following nations (Nazi Germany, Imperial Japan, USSR and USA) possess less than a dozen usable atomic weapons, with a yield equivalent to the "Fat Man" bomb of 21 kt, prior to September 1939. Since an air deliverable A-bomb was not possible for any aircraft at the time, it would need to be a sea or land based weapon.

TOPIC: How would these nations use atomic weapons in the early years of the war, based on the same type of delivery platforms available for that era?

Does this still assume only the US knows about Plutonium? Uranium bombs are a different thing. The Hiroshima bomb was enriched uranium. The Nagasaki bomb was Plutonium. This makes a big difference in production techniques and how many bombs would be available and how much future production a country could expect.
Also note, that over half the weight of the two US weapons dropped on Japan was an armored shell to make the bomb "flak proof." That is, those bombs were designed where if the plane took flak damage the bomb would survive anything other than a direct hit. This means that it would be possible for the pre-war bombs you propose to weigh as little as 3,000 or 4,000 lbs. at most.

Could the IJN use a merchant ship to carry one of the bombs into Pearl Harbor and detonate it next to Battleship Row, or any other military/civilian target of convenience? Would the Japanese use an A-bomb on Singapore as well with 85,000 British soldiers in garrison? Maybe the Chinese National Army would have been destroyed on the battlefield with a few atomic blasts?

It would be virtually impossible for a Japanese ship of any sort to enter Pearl Harbor and do what you propose. There was an "Exclusion zone" off the entrance of the harbor guarded by US Navy ships like the destroyer Ward. Any ship or submarine entering the area was subject to being stopped and examined well outside the harbor. The Navy ships could also attack on sight any submerged submarine.
The harbor itself is only for the military. The commercial harbor is at Honolulu. There are two sets of nets across the harbor entry, and there are both submerged mines that are command detonated as well as a set of hydrophones and magnetic detection devices on the bottom of the entry channel that are monitored.
While attacking Honolulu is certainly possible, that would be a purely civilian target. Likewise, Singapore is a civilian target. The British naval base is miles away on the other side of the island and inaccessible to civilian shipping without passing through the British defenses.

The Nazi government could send a diplomatic train to Moscow with a few atomic devices stowed aboard; the daisy-chained atomic blasts would ensure Moscow resembled Nagasaki or Hiroshima. Would the Germans nuke Warsaw, Paris or London?

I would think Germany would have made a much greater emphasis on developing an aircraft that could deliver such a weapon, like an earlier Me 264. I'd expect other countries with nuclear weapons to do likewise (Soviet improved Pe 8, improved XB-19, etc.) I'd also think that if only Germany possessed nuclear weapons and France and Britain did not (which seems strange since Japan has them) that Hitler would use them for intimidation or even in attacking both countries. Obliterating Paris and London would seem far more likely early on.
This is particularly true if Hitler knew that neither country could retaliate. Both would likely resort to mass gas attacks on Germany using mustard gas if this did happen.
The US might also sell or give Britain or France nuclear weapons, particularly if the US knows they can produce more. Then Germany gets what it gave. I could see the Ruhr in particular being wiped out. Hamburg would be an excellent target too. These aren't deep into Germany so hitting them would give the Luftwaffe little time to respond.

How would the USSR have employed these weapons, would they be used on their own soil in an attempt to stop the German invasion or would the Red Army go on the offensive first and attempt to conquer Europe?

That would depend on how many they thought they could produce and at what rate. It could be sufficient that the Soviets simply use them for intimidation and the Germans don't invade at all. This would be far more likely if Germany were involved in a nuclear war with France and Britain. Such a war between the three would pretty much put Germany out of the running to invade the Soviet Union later on.

We know the USA used 2 weapons at the end of the war, when they were trying to force the Japanese to finally surrender. However, if they had the A-bomb sooner, would it be used on Tokyo at the earliest possible opportunity?

Depends on Japan's actions. Where do the Japanese use theirs? China? Maybe on the Russians? I'd say the second Japan let loose a nuke on anyone the US would have been at war with them, and the US would have figured out a way to drop one or more on Japan proper.

[Takao]

The US had the XB-15 in 1937, and the XB-19 in 1941, both would have been capable of carrying Little Boy.

The XB-15 were not built in any numbers, and the XB-19 did not make its maiden flight until 27 JUN 1941. So they were not available for use, by the time the war began on 1 SEP 1939.

Sigh...There were also no atomic bombs in 1939.

But, wait, now there are, and the B-15 is the only aircraft in the world that can carry it. Certainly, the US will make more of it's atomic bomber, and continue to refine it.

Wheen you only have 2 bombs, you only need 1 bomber. As such, mass production is immaterial as to the carrying capacity. The XB-15 was avail available, and could carry an atomic bomb.

And to the B-19, who's to say that the B-19 could not have been started earlier just as the atomic program was.

[Takao]

In 1943, the US planned on dropping the atomic bomb on the IJN anchorage at Truk Lagoon. It was th bought to be the safest target from a secrecy stand point - The lagoon was deep enough to make recovery difficult to recover parts of a dud. The greatest fear was reverse engineering.

But with everybody and their uncle now having atomicsb secrecy does not matter.

[Volyn]

Good comments all -

I proposed less than 12 bombs for all 4 nations since it would make their use more thoughtful and intentional. There are many potential targets but with limited bombs those targets have to become prioritized.

I am assuming the atomic weapons that would have been developed prior to the start of WW2 would have been crude designs that would not have allowed them to be fitted to aircraft. I know it seems a bit absurd to have a bomb and no plane, but I am trying to gauge how these governments would decide when and where to strike based on the real weapon platforms that were available, and what would have been their calculus?

It seems that Japan and Germany would not have hesitated to use these weapons in a first strike capacity, but would the USSR and USA do the same or would they be used more defensively at first?

[OpanaPointer]

A barely portable bomb would have limited applications. The scenario would have to be nearly ideal before use would be considered. And use defensively would imply use on one's own territory.

[Volyn]

A barely portable bomb would have limited applications. The scenario would have to be nearly ideal before use would be considered. And use defensively would imply use on one's own territory.

Exactly, so how do governments employ such a device under conditions that they would consider ideal?

Ships, trains and armored vehicles seem to be capable of sending these devices to a target, and remember nobody would know that an A-bomb was aboard, especially if they sent several decoy vessels to help distract.

[OpanaPointer]

Delivery is going to be difficult if the bombs are crudely built and bulky. So what would it weigh?

[Volyn]

Delivery is going to be difficult if the bombs are crudely built and bulky. So what would it weigh?

Instead of weight let's keep it simple and assume the size of these devices would be too large for the available aircraft, but they would be still be small enough to be moved about by other means of transportation. It is too easy to say they'll "drop a bomb" but what if you cannot drop it, how else could they be used?

I have doubts that the USSR's political leadership would use these weapons in a preemptive offensive manner, but I could see them use it in a static defensive posture. For example, maybe they would secretly store them in cities like Smolensk or Korosten, so if in the event that they fell to the enemy, those bombs would be remotely detonated and kill whomever occupied the city.

I could also see the Japanese employ these devices in China against the National Army on the battlefield, maybe using armored trucks as the mode of delivery.

The Germans seem to be ready to kill anyone, but they did not start the war off like that. I doubt that Hitler would have used these weapons immediately against civilian centers and capital cities. However, since U-47 was able to penetrate Scapa Flow on 14 OCT 1939 it seems like this would be a likely method to use an atomic weapon aboard a U-boat, and destroy the harbor.

We know the USA will use A-bombs offensively, but it was done as a last resort at the end of the war. Would Roosevelt have the will to use atomic weapons if they had been available sooner?