Germans in WWII having Iowa class battleships

[Dave Saxton]

.... I/m pretty sure the 40mm Bofors mounted on the Iowas were radar directed...

Nope only optics. The British had Type 282 during the war but it wasn't very effective. They were trying to develop Type 262 at war's end but it never was successful and was finally abandoned during the late 1950s.

I looked up some numbers and battleship will need all those rounds and more. The number of rounds per aircraft shot down was in thousands for heavy flak but better for light flak-during good visibility. At night and poor visibility the ratio could be 10 fold greater.

I don't see the 40mm battery, which is the main difference here, no matter how impressive, being that much of game changer over a Prince of Wales or German heavy ship during 1941. (The Scharnhorst performance posted by Thorsten is rather impressive for 1940 though)

[alecsandros]

At night and poor visibility the ratio could be 10 fold greater.

... At the same time, the chances of the torpedo planes to score hits would drop very much in poor visibility...

I don't see the 40mm battery, which is the main difference here, no matter how impressive, being that much of game changer over a Prince of Wales or German heavy ship during 1941.

Well, the Iowas were equipped with 20 quad mounts... Prince of Wales had 4 octuple mounts...

The problem for the Swordfishes would be their speed: approaching that slow meant the AA systems would have plenty of time to destroy them all... 60-70 seconds of non-interupted fire, is a lot for battleships that can output 11000 + AA shells/minute at ranges > 1km...
In comparison, the Nell torpedo bombers that destroyed the Prince of Wales were approaching at ~ 300km/h, so twice as fast as the Swordfishes. This gave the AA gunners maybe 40 seconds of firing before the planes got to their launch positions... The output of the medium+heavy flak of the Prince of Wales was about 5000 shells/minute. So in 40 seconds, they could put up a maximum of ~ 3300 shells.

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And If there were 2 Iowas operating together, than the combined output would be ~ 22000 shells/minute for medium+heavy flak, so wipe out for the Swordfishes...

cheers,

[alecsandros]

Doing further reading on the matter,
I came across the following comparisons:

Fletcher class destroyers: 2x4 40mm Bofors; 6x2 20mm Oerlikon, 5x127mm guns. [output beyond 1000m: 1250 shells/minute; total output with Oerlikons: 4850 shells/minute]

New Orleans class heavy cruiser: 4x4 40mm Bofors, 19x1 20mm Oerlikon, 8x130mm guns. [output beyond 1000m: 2400 shells/minute; total output with Oerlikons: 8180 shells/minute]

Iowa class battleship: 20x4 40mm Bofors, 49x20mm Oerlikon, 20x127mm guns [output beyond 1000m: ~ 11000 shells/minute; total output with Oerlikons: ~ 25700 shells/minute]

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For targets between 1000-4000meters, a single Iowa class battleship could put up more shells in the air than 3 Fletcher class destroyers and 2 New Orleans class cruisers combined... And at close range, the AA volume was similar to 2 destroyers and 2 heavy cruisers...
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[Dave Saxton]

But historically such output was never realized in practice. In action on Nov 25th 1944 the Iowa only expended 78 rounds of 5" and a total of about 6,000 rounds of combined 40mm and 20mm in ten minutes. Yet despite being hit by both Iowa and New Jersey three Japanese aircraft crashed the Intrepid, Cabot, and Hancock. Metal aircraft are in fact easier to bring down by light flak than the fabric and wood and wire Swordfish (I won't go into the complex problems of radar ranging and rating them here). In a period of 3 weeks in March 1945 Iowa and New Jersey expended only 738 rounds of 5", 2025 rounds of 40mm, and 3754 rounds of 20mm.

The problem was target aquisition. SK air warning radar had numeruous blind spots depending on the range. At night or in poor visibilty the Iowas could be shockingly toothless in terms of AA. On the 12th of June 1944 in a night attack the Japanese got torpedos into the water with out taking any hits from 5" or 40mm. Fortunately through some good ship handling no torpedo hits were scored, but it finally fell to the 20mm guns to down one aircraft after the torpedo was launched.

The British Swordfish had to use ASV radar to acquire the target and to launch their torpedos vs Bismarck in both historical cases. During the Victorious attacks the British popped out the clouds three times (the first two against the US Coast Guard cutter and Norfolk), having located a target by radar, to attack giving the target as little time as possible to develop an effective Flak defence.

[alecsandros]

.. Clearly the outputs were not continous. But they represented the AA capability of the ship.
I doubt a Fletcher class destroyer actualy put up ~ 5000shells/minute in any single event... So all the above capabilities are statistical of course.

There were situations though when US battleships expended massive amounts of AA ammo.
One such case was the North Carolina at Eastern Solomons (10.000 shells and 9000 maching gun rounds). Another is South Dakota at Santa Cruz (60.000 shells). And there are others also.

Fighting against Kamikazes was different to fighting incoming torpedo bombers. The kamikaze attacks were many times performed at speeds of 400, 450, 500km/h or even more. By comparison, the torpedo bombers flew at 300-320km/h in the final attack phase. The Swordfishes approched at 160-180km/h. They also had a more stable trajectory.

Imagine those 3 planes that you mentioned above flying at 160km/h. And Iowa and New Jersey opening fire on them...

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From USS Washington's anti-kamikaze report:

"The major defect in defense against suicide plane attack is inability to identify and get on the target while there is still time to put up fire of effective volume and accuracy. Concentration on training lookouts and fire control teams by conducting all recent antiaircraft target practices as 'surprise' practices, has produced some improvement and may be expected to"

[RF]

I think that, in the face of such a threat the US would not only deploy it's own Iowas to the Atlantic, but also several new-construction CVs and CVLs. This would probably have delayed US operations in the Pacific. The German BBs would have been brought-down, but not before seriously complicating Allied operations & planning in both theaters.

The last sentence in this quote depends on other factors.

If Germany is at war with the US then Germany requires weapons that can strike the heart of the US homeland - trans-Atlantic heavy bombers and missiles.

[paul.mercer]

Gentlemen,
A very interesting situation although I doubt very much that Hitler would have allowed all of them to go to sea at once. If they did then the RN has a serious problem, not enough aircraft carriers and the ones that the did have had obselesant aircraft, ( I know they hit Bismarck but if all four were together supported by destroyers I don't think any would get through). Also, if they all came out together then the RN had nothing capable of stopping them, they could probably take on and sink the entire home Fleet whilst incurring little damage to themselves.
Of course had our spies reported the building of such ships the RN would have without doubt responded by outbuilding the Kreigsmarine with equal or more powerful ships.

[RF]

Also, if they all came out together then the RN had nothing capable of stopping them, they could probably take on and sink the entire home Fleet whilst incurring little damage to themselves..

I don't think this is entirely true. You don't have to get the entire Home Fleet or Force H to engage them to effect an attempt at destruction, an attempt as you say is likely to fail.
No, I would use indirect methods to deal with these ships rather than outright confrontation. In particular these vessels will need a substantial supply train to keep themselves at sea. So I would go for their supply ships and sink the lot.
British submarines would be detailed to torpedo them in home waters. I would use Bomber Command to raid them in harbour. I would seek to split the German Iowa's up and try to diamage one so that it can either be picked off if it is on its own, or let it be an encumberance to the rest of them if they choose to shepherd it home.
There are quite a few diversionary tactics that can be used to defrade the strength of that force.

[Wordy]

What would the RN be doing in the 2+ years that it would take for the Germans to build an Iowa? Building the Yamato's big brother perhaps?

[alecsandros]

Perhaps completing the Lions ?

They would be tough beasts, with 9x16" guns in 3 triple turrets, 380mm main belt, 150mm main deck and 28kts speed.

Basically a KGV with 9x406mm guns instead of the 10x356mm arrangement...

[RF]

I think building some large aircraft carriers would be a good idea, as well as the big battleships.....

[alecsandros]

I think building some large aircraft carriers would be a good idea, as well as the big battleships.....

Indeed.

An interesting question would be if a fleet carrier would benefit Britain in combating the German Iowas to the same extent as building the heavy battleships ?

[dunmunro]

swordfish attack profile against Scharnhorst (Utsire 21.07.1940) one year before "Rheinübung"
contact holder distance 19 km 170 degrees
torpedobombers gather over the clouds ahead and abeam to port of the ship
breaktrough the clouds in a tailspin until a heigt of 80 - 30m was reached in somewhat above 2000 m distance
releases distance about 1800m - 1200m distance

three out of six swordfish were shot down by Scharnhorst.

swordfish attack profile Utsire.png

Scharnhorst was escorted by 4 destroyers and 4 destroyer escorts. Only two Swordfish were downed, both after releasing their torpedoes.

[RF]

Indeed.

An interesting question would be if a fleet carrier would benefit Britain in combating the German Iowas to the same extent as building the heavy battleships ?

Well, one obsolete small carrier and one obsolete stringbag was enough to nail Bismarck.

The problem for the Germans operating a group of Iowa or any other class of battleships is that carrier aircraft are unlikely to sink them outright, but can cause enough damage for one or more of the battleships to be rendered as lame ducks.... either that vessel is sacrificed or it becomes an encumberance to the rest of the fleet.

Carriers on their own aren't enough. They need other forces and tactics to reinforce their degrading effect. Sinking the German supply ships when the battleships are far from home is another degrading tactic that helps carrier attack.

[alecsandros]

Well, I am quite confident about Iowa's AAA gunnery... 80 Bofors and 49 Oerlikons with 20 radar guided heavy AA guns was a lot... And if 2 IOwa's woudl be operating together, they would put up an umbrella of fire from nearly 300 AA guns...

Not enough to stop a massed air attack (with, say, 40-50 bombers), but enough to deal with an incoming squadron of 8-12 (slow) attackers.

I've been reading about hte Channel Dash lately, and the number of Swordfish and Beaufort destroyed by AA artillery was about 50% of the RAF losses that day (14 out of 29)

And that allthough the German formation did not have a massive AA defence that 2 Iowas would have...