Bomber Command failure at Urft Dam.

[tcolvin]

Can anyone provide factual insight, or a source for factual insight, into the failure of Bomber Command (BC) to destroy the Urft and Roer River dams in December 1944.

Eisenhower ordered these earthwork dams destroyed with absolute priority.
Destruction of earthwork dams was surely within BC capabilities using Tallboys delivered at night or in any weather with H2S.
As everyone knows, BC had successfully destroyed the concrete Ruhr dams.

The Diary of General Courtney Hodges, GOC 1 USArmy, has these entries;
Nov 30; After consistently refusing, the RAF finally consented to blow the Roer dams, scheduled for the morrow, weather permitting
Dec 1; Attack postponed until tomorrow
Dec 2; Attack again postponed
Dec 3; Bombing of Urft dam a 'dud'
Dec 5; Hodges told RAF had bombed for third time but without results
Dec 7; Tomorrow RAF to make fourth attack
Dec 8; RAF bombed but made impressions the size of a dollar. Unknown if RAF would try again
Dec 11; RAF attacked with 230 Lancs. Aerial recce showed one hit in center with water spilling over it but dam not destroyed. Road access across it destroyed in two places
Dec 12; RAF mission postponed until tomorrow due bad weather
Dec 13; RAF mission scrubbed due bad weather
Dec 14; RAF's fifth attack again postponed

Terraine in 'The Right of the Line' doesn't mention the matter as far as I can see.

Saunders wrote; "In (December) BC went out on nineteen occasions by day, thrice against the dam at Urft. These three attacks were made at the request of the US9Army, which by then had reached the River Roer. If they crossed it, the enemy, who controlled the dam and another at Schwammenauel, might destroy these and thus release the floodwaters and cut off the Americans. The dams had therefore to be broken beforehand. The attacks were carried out on the 4th, 8th and 11th, but without appreciable results".

The Bomber Command War Diary has these entries;
3 Dec; 183 Lancs + 4 Mosquitoes to Heimbach. No bombs dropped.
4 Dec; 27 Lancs + 4 Mosquitoes bombed out of 200 sent to Urft dam.
5 Dec; 56 Lancs, but only 2 bombed.
8 Dec; 205 Lancs to Urft, Schwammenauel and Paulushof dams.
11 Dec; 233 Lancs + 5 Mosquitoes to Urft dam.

One source, which I have not recorded, states that after the Dec 4 raid the RAF protested to Ike who told them to keep trying.

The result of not destroying the dam was as predicted. When Operation Veritable started on February 8, 1945 it was without the other half of the pincer movement, Operation Grenade, which was held up for ten days by the Germans blowing the Urft and other dams and making the Cologne plain impassable. The result was a bloodbath in the Reichswald and Hochwald as 2 Canadian Army (with almost the entire British army under command) had to face the entire German defences without assistance from 9USArmy held up behind the flooded River Roer.

So why was BC at the height of its powers ineffectual?
Was it sabotage by Harris in his feud with Portal?
Was BC really only interested in area bombing the few unburnt cities left like Dresden?

Tony

[Kutscha]

Note the 'bad weather' mentioned numerous times.

[tcolvin]

I did and do note the bad weather.

Bad weather should therefore have argued against using 1,000-lb medium capacity bombs dropped by sight, which is how I suspect BC approached the problem of the Urft Dam.

Surely a better solution would have been the use of Tallboys as used by 617 Squadron on September 23, 1944 to breach the Dortmund-Ems Canal.
617 Squadron bombed by sight, as I understand it, but used appropriate ordnance.

The Urft dam situated at the end of a large stretch of water, would surely have been a natural for H2S MkIII which could operate accurately at night or in bad weather.

The impression given is that BC did not try very hard to overcome the problem, and therefore failed.

The reason for lack of enthusiasm would have been reluctance by Harris to divert BC from the destruction of cities to what he called panaceas, such as the oil plan and army support/destroying dams.
So Harris might have engineered a failure to break the dam so he could tell Ike he was wasting his time ordering BC to provide support to the army.
Success in breaking the dam would only encourage Eisenhower to ask for more.

But that is surmise.
What I am seeking are facts and insight.

Tony

[Bruce Dennis]

Were Tallboy bombs made to order? If so, then whatever was in stock would have been already allocated, and the lead time for production may have precluded their use in an urgent assignment.

I have seen them described in different ways, while retaining the 'MC 12,000 lb' name. For example, some used against U-boat bunkers were called 'concrete busting' bombs, which implies specialist applications, perhaps merely in fusing but possibly in construction. This could be another factor in whether or not existing stocks were suitable for the destruction of the dams in question.


Bruce

[tcolvin]

Good point, not covered in http://en.wikipedia.org/wiki/Tallboy_bomb

But I note this from this article;
- 854 were manufactured by Vickers.
- When dropped from 20,000 ft (6,100 m) it made a crater 80 feet deep (24 m) and 100 feet (30 m) across and could go through 16 feet (5 m) of concrete.
- The weight of the Tallboy (approximately 12,000 lb) and the high altitude required of the bombing aircraft meant that the Lancasters used had to be specially adapted. Armour plating and even defensive armament were removed to reduce weight and the bomb-bay doors had to be adapted. Even then the Lancaster was not capable of reaching the bomb's intended dropping height of 40,000 ft (12,200 m) but only around 25,000 (7,700 m). At the same time N0. 617 Squadron trained in the use of a special bombsight the Stabilizing Automatic Bomb Sight (SABS). For accuracy multiple corrections had to be made for temperature, wind speed, etc. However it was only effective if the target could be identified and several missions were canceled or unsuccessful because of difficulty in accurately identifying and marking the targets.
- For use on underground targets, the bomb was fitted with three separate inertia pistols. These triggered detonation after a pre-set delay, which gave the bomb sufficient time to penetrate the target before exploding. Depending on mission requirements, the time delay could be set to 30 seconds or 30 minutes after impact. In order to guarantee detonation, a total of three separate Type 47 long delay fuzes were fitted inside the rear of the bomb. This dramatically improved reliability of the weapon: even if two of the fuzes failed to function, the third would trigger detonation. Despite this elaborate fusing system however, at least one Tallboy failed to explode during the second attack on the Sorpe dam and was found during repairs in late 1958 when the reservoir was emptied.
- Tallboys were not considered expendable and if not used on a raid were to be brought back to base rather than safely dropped in the sea. The value of the weapon offset the additional risk to the aircrew. Given their high unit cost, Tallboys were used exclusively against high-value strategic targets which could not be destroyed by other means.

Comments and questions;
- Tallboys were used on the Sorpe dam, so it was definitely approved ordnance for earthdam-busting. So one uncertainty is removed.
- Did 617 Squadron have a monopoly? They used a special sight and had specially modified Lancs, so that suggests they were the only approved squadron.
- But perhaps although a special sight was necessary for hitting buildings and ships like the Tirpitz, a dam is such a large structure that it did not need such accuracy. Perhaps the earthquake effect of one Tallboy falling anywhere on or near the Urft dam would have shattered it?
- On December 3, according to the BC War Diary, 190 Lancasters dropped markers but no bombs on the Urft Dam'. What was that about? Perhaps BC was after all trying to find a way of using Tallboys on the Urft Dam.

Does anyone know of an RAF source for any contemporary or memoir discussion about destroying the Urft Dam?

Tony

[Kutscha]

617 did drop Tallboys on the the 8 and 11 Dec.

http://www.dambusters.org.uk/docs/recordbook.pdf

[tcolvin]

Thank you for that lead, Kutscha. Much is now clearer.

It appears that 617 Squadron and 9 Squadron (from October 1944) were the only ones trained to drop Tallboys, of which about 700 were used during hostilities.

The Roer Dams, like the Ruhr Dams, consisted of two types; the walled masonry Urft dam (like the Möhne and Eder), and the earth-covered concrete-cored Schwammanauel dam (like the Sorpe).
In December 1944 BC handled each differently, but both unsuccessfully.

The Urft is a walled masonry gravity dam, 58m high and 226m long.
It was allocated to 8 Group, which presumably included 617 and 9 Squadrons.
The following excerpt argues that Upkeep (the bouncing bomb) was more appropriate than Tallboy for destroying such dams, but Upkeep was no longer operational in December 1944.
“Most interestingly, the (12,000-lb, 6-ton Tallboy) bomb was used against dams (one of the principal targets for the big bombs from their inception, of course). The Kembs Barrage (that is a weir) in Alsace and part of the Rhine canal system, was successfully breached on 7th October 1944, thus preventing the Germans using it to flood U.S. troops approaching from Belfort. Uniquely on this raid, the Tallboys were dropped at low level for accurate positioning; use of Upkeep again would have been more appropriate, but for the Lancasters but there was not time to train the new crews for delivery of the weapon. The Sorpe Dam was also attacked with Tallboys (by 9 Squadron conventionally from 14,000ft) on 15th October 1944 and hit by two Tallboys (plus several near misses) but not breached (one Tallboy was found in the mud when the dam was partially drained in 1958, and successfully defused). Three raids were also mounted against the Urft Dam, 30 miles SW of Cologne, during December, again to prevent it being used to flood troops, and the lip of the dam was damaged, but the Germans prevented further damage by lowering the water level.”
http://www.sirbarneswallis.com/Bombs.htm

Upkeep was not appropriate for an earth dam with a concrete core, as was discovered when the Sorpe Dam survived two direct hits. Again this excerpt from the same website; “Sorpe Dam: Unlike the Möhne and Eder Dams which were walled dams, the Sorpe was constructed of a concrete core flanked by earth banking on both sides. Different tactics were thus employed against the dam, which was to be attacked along its crest, and the mine dropped without spin. McCarthy made the first attack, making nine dummy runs as the target was covered in mist; on the tenth run, the mine was dropped and exploded on the dam crest. Brown also made several dummy runs, dropping his mine on the sixth run. It also exploded on target, but although the crest was damaged, the dam was not breached and no seepage through the core (as hoped for) resulted. The damage to the crown of the dam, however, required the Germans to half empty the reservoir to effect repairs, so there was some water loss as a result of the attack.”
As seen above, the Sorpe Dam was also proved resistant to Tallboys.

The Schwammanauel Dam like the Sorpe is a massive earth dam with concrete core, and the second largest barrage in Germany.
It was given to 3 Group to destroy, and presumably they used 1,000-lb medium bombs without effect.

In conclusion, then, it appears that BC lacked the means in December 1944 of destroying dams like the Sorpe and Schwammanauel until the introduction of the 22,000-lb (10-ton) Grand Slam. “Its first use was against the Bielefeld Viaduct; 3,000 tons of bombs (including Tallboys) had already been dropped on it with little result, but Grand Slam brought it down on 14th March 1945 (the first Grand Slam had been test dropped in the New Forest the day before). Grand Slam was used against similar targets to Tallboy (often a raid would include both types of bomb), and again caused remarkable destruction wherever it was used - the Arnsberg, Arbergen, Neinburg and other bridges were also to be felled by the bomb. In total, 41 Grand Slams were dropped during the war.

After BC had withdrawn Upkeep (the bouncing bomb) they then lacked the means of destroying walled masonry dams. They could find no means of placing Tallboy alongside the dam wall. Masonry walled dams are presumably resistant to earthquakes.

The bottom line is that BC lacked the means of destroying either the Urft or Schwammanauel Dams. But they did try valiantly - that is clear.

Does anyone know whether Grand Slam was ever used against a walled masonry dam, and if so with what result.

Any comment or observation on the above conclusion, or on anything else, would be most welcome.

And again thank you, Kutsch and Bruce Dennis, for your help.

Tony

[tcolvin]

A final question.
The 617 Sqn ORB states that they found the Urft Dam and orbited it in almost full cloud looking for a sighting through GEE.
As I recall, GEE was said to be so accurate that a Mosquito using it could drop a bomb down a chimney stack in the Ruhrgebiet, which was close to the limit of GEE's range.
617 Sqn, however, did not drop Tallboys with GEE but only bombed visually, returning their valuable bombs to base if visibility failed for a proper run-up. I wonder why.
And as I wrote earlier, H2SMkIII would seem a natural bomb sight for use on dams, but the 617 ORB does not mention its use.
Any insight into these matters, anyone?
Tony

[Kutscha]

Yes, and the Norden sight was said to be able to put a bomb in a pickle barrel.

from http://jproc.ca/hyperbolic/gee.html

After final alignment of the pulses, a timing display was switched in and the time delays for each slave visually counted. This could be done accurately because the signals were switched off and a noise free display was obtained. For various reasons, time was not counted in microseconds (as was done in Loran) but in 'Gee units' where one unit was equivalent to 66.66 microseconds. A measurement accuracy of 1 microsecond was achievable, representing a position line accuracy of about 150 meters at best; two such providing a fix accuracy of around 210 meters , although other errors in the system might double this. At longer ranges, 350 miles for example, the error ellipse was about 6 miles by 1 mile. While not remarkable by today's standards, it was revolutionary at the time and far in advance of any other method of fixing.

[Nick Beale]

Originally Posted by tcolvin

A final question.
And as I wrote earlier, H2SMkIII would seem a natural bomb sight for use on dams, but the 617 ORB does not mention its use.
Any insight into these matters, anyone?
Tony

Possibly the physical constraint of fitting an H2S radome to the belly of an aircraft carrying a Tallboy — would there be room for both, or would the presence of several tons of steel right in front of the radome interfere with the radar, perhaps?