WI: 'Tall Boys' & 'Grand Slams' used by the US against & Japan?

[Giant Man Eating Rabbits]

What if the US were interested in the British 'Tall Boys' & 'Grand Slam' bombs to be used against Japan and started manufacturing them?

(this isn't about the M110 T-12 as it came after the war)

Would any of the USAAF aircraft be capable of carrying anything like this even if modified?
What if they used them against military targets in mainland Japan?
What if they were used against the tunnel complexes in Iwo Jima and Okinawa?
What if they were used to attack the IJN ships Yamato and it's sister?
How successful would they be?
Would they be able to influence the war in any way from OTL?
Would they be able to be used against targets in Europe or would they leave that for the RAF?

 

[naraic]

I'm pretty sure there was a B29 version modified to carry grand slam bombs and they did use the tallboy operationally during korean war.

I'm sure there would be viable targets but these bombs were in fairly short supply so its not going to have a decisive influence.

I'd say their use would be limited and to high value targets. I'm sure they would be relatively successful in what amounts are used but its not likely to change the war.

 

[Nivek]

What if the US were interested in the British 'Tall Boys' & 'Grand Slam' bombs to be used against Japan and started manufacturing them?

(this isn't about the M110 T-12 as it came after the war)

Would any of the USAAF aircraft be capable of carrying anything like this even if modified?
What if they used them against military targets in mainland Japan?
What if they were used against the tunnel complexes in Iwo Jima and Okinawa?
What if they were used to attack the IJN ships Yamato and it's sister?
How successful would they be?
Would they be able to influence the war in any way from OTL?
Would they be able to be used against targets in Europe or would they leave that for the RAF?

Even OTL with two atom bombs, the hardlines wanted to fight, so TB and GS as good they're, are just like the tokyo firestorm, they will refuse to admit defeat

 

[Peg Leg Pom]

Even OTL with two atom bombs, the hardliners wanted to fight, so TB and GS as good they're, are just like the tokyo firestorm, they will refuse to admit defeat

Unless you know where the bunker they're hiding in is. A Tallboy or Grand Slam on their head would end their opposition pretty quickly.

 

[Giant Man Eating Rabbits]

Unless you know where the bunker they're hiding in is. A Tallboy or Grand Slam on their head would end their opposition pretty quickly.

How effective on Iwo Jima or Okinawa would they be?

Would they be able to penetrate deep enough to cause any damage and could they cause enough concussion to kill enough enemy troops to make a difference to the battle?

 

[Sekhmet_D]

What if they used them against military targets in mainland Japan?
What if they were used against the tunnel complexes in Iwo Jima and Okinawa?
What if they were used to attack the IJN ships Yamato and it's sister?

A Tallboy dropped onto the huge blockhouse sitting atop Turkey Knob would have flattened it into the dirt. At the very least, you're going to see the Iwo death toll reduced by several hundreds.

Conventional carrier aircraft strikes would suffice for Yamato and Musashi, but Tallboys against the remnants of the Japanese Navy anchored at Kure, where they were berthed in such a way that precluded torpedo use, is a very interesting prospect.

 

[CaptainCalvert]

If atomic bombs weren't ready, these would be potentially useful for doing major damage to bunkers or very hard targets. How accurate were they from the kind of altitude where fighters and flak were largely ineffective?

 

[Court Jester]

Combination of mass and aerodynamic shape meant they were quite accurate from high altitude.
Tallboys and Grandslams against tunnel complexes would collapse a section of tunnels near the point of impact, which in turn would cause over-pressure in remaining parts of the complex killing or wounding the defenders through combination of pressure and suffocation, while also marking all exits through clouds of ejected dusts, so you can bombard them with artillery or strafe with fighters, to kill surviving soldiers, crawling out so they can breathe.
Best targets in mainland Japan would be various railway bridges and viaducts, with mining campaign crippling coastal shipping, disruptions of railway traffic would have catastrophic consequences and since Tallboys and Grandslams destroy foundations of bridges and viaducts, repair is much more difficult.

Keep in mind though that these bombs were not made for piercing reinforced concrete, they had some success in it, but against hardened targets the most effective hit was a near miss, which would undermine the foundations.

 

[The Wooksta!]

I’ve a 72nd Lancaster, with the far east mods, converted to a B.I special for operations against Japan, but it’s far from completion. I did finish the similar Lancaster B.VI, although that got SEAC roundels.

 

[Sekhmet_D]

How accurate were they from the kind of altitude where fighters and flak were largely ineffective?

Japanese air defences were nowhere near as formidable as German ones. The bombers can afford to go in lower.

 

[jlckansas]

You don't want to go lower you want to go higher with these bombs for accuracy and penetration.

 

[Rolf]

To its not a question of could they, or should they, but why bother?

Napalm and incendiaries had a much greater affect in the island campaigns and destruction of the Home islands.

 

[jlckansas]

Tall Boys and Grand slams would be good attacks against the RR tunnels, mines, and the fleet at anchor. Everything Billy Mitchell did with his demonstration against the Ostfriesland would be magnified 10 fold at least in places like Kure.

 

[sonofpegasus]

If you do a 617/19 Squadron raid such as sunk Tirpitz the effect within an anchorage with concrete Basins will be magnified. Hit the wharf close along side and tons of concrete will batter the side and bilge of the ship. Land in the water within the basin and the shock wave will be reflected by the walls.
A B29 could I believe carry two tall boys, one under each wing or a Grand slam on the centreline. This modification was carried out by Boeing for use against mainland Japan but was never deployed.
Somewhere in a US archive there might even be a target list!

 

[Captain Seafort]

Everything Billy Mitchell did with his demonstration against the Ostfriesland would be magnified 10 fold at least in places like Kure.

An order of magnitude more than fuck all is still fuck all.

 

[PhilKearny]

Mandatory photo

 

[The Wooksta!]

Another irony is that I have an assembled B29 that at some point was going to get a respray, British Pacific Fleet markings with 9 Sqn codes (617 is soooo passe…) and a pair of BFO bombs underneath.

My earlier post intrigued me enough to dig out said Lancaster. Lot of masking, but easy enough to finish. I then dug out a spare Hasegawa kit an located most of the resin bits to turn it into a B.I special, although this would go in overal bare metal to lessen the chances of US gunners shooting it down.

 

[Court Jester]

Napalm and incendiaries had a much greater affect in the island campaigns and destruction of the Home islands.

Incendiaries do nothing against bunkers and tunnels, they also don't collapse bridges and viaducts

 

[MKD]

the yanks are gonna need some Lancaster bombers! Of course, the USAAF didn't really have the accuracy they pretended to have so would need the RAF to do the actual precision work....................

;-)

 

[sonofpegasus]

Calling 617 squadron with Avro Lincolns !

Scaling the bombs on the B29 picture, those are two tall boys at about 12000 lbs each. I do not think that the B29 could lift two Grand Slams for a Total weight of around 44,000Lb or in other words 20tons,
A single Grand slam on the centreline , yes, two on the wings, nope! I think not,