Bomber Command failure at Urft Dam.
 

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

Re: Bomber Command failure at Urft Dam.
 

Note the 'bad weather' mentioned numerous times.

Re: Bomber Command failure at Urft Dam.
 

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

Re: Bomber Command failure at Urft Dam.
 

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

Re: Bomber Command failure at Urft Dam.
 

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

Re: Bomber Command failure at Urft Dam.
 

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

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

Re: Bomber Command failure at Urft Dam.
 

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

Re: Bomber Command failure at Urft Dam.
 

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

Re: Bomber Command failure at Urft Dam.
 

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.

Re: Bomber Command failure at Urft Dam.
 

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?

Re: Bomber Command failure at Urft Dam.
 

H2S in 1944 was not what we would call a precision targeting device today. It allowed Bomber Command to find larger cities, but nothing as small as a single dam. Target markers dropped using H2S often had errors of up to a mile, but at the time that was a big improvement over the errors of tens of miles using purely visual methods early in the war.

It was more a navigation aid than a bomb sight. Postwar refinements allowed developed versions of H2S to be used as a bomb sight, as in the runway bombing in the Falklands.

All the pictures of 617 Lancasters I can find on the web do not show an H2S fairing.

Re: Bomber Command failure at Urft Dam.
 

Thanks Kutscha, Nick and Bill for providing evidence that neither H2S nor GEE were accurate enough for 617 Squadron.

That leaves Oboe and GEE-H, both of which gave an error radius of 110 metres at 400 kms (120 yards at 250 miles), said to be as good as optical gunsights.
Is there any evidence, I wonder, that 617 Squadron used either Oboe or Gee-H when dropping Tallboys on targets obscured by cloud?

By the way, and not off-topic, 2TAF was at that time experimenting with using one of their four AMES Type 25 convoys for controlling blind bombing by Bombphoons.

In July 1944 the RAF had formed and begun training the first MRCP (Mobile Radar Control Post), which was a Modified SCR.584. It was shipped to Erp in Holland in October and used for the first time to direct (not control) Typhoons on November 11 in the attack on Venraij when the MRCP put 6 aircraft of 247 Squadron on the target which however they missed. But on the same day 5 aircraft of 137 Squadron were directed to a battery 5 miles SE of Goch and claimed the destruction of 2 guns. The month's trial with 83 Group had shown that the MRCP had some small benefit in directing pilots in conditions of poor visibility, but was limited by short range. The MRCP was then transferred to 84 Group for experiments in blind bombing.
Its mean error of 350 yards indicated that its best application with Tactical Air Force Fighter Bomber groups was the blind level bombing of targets such as villages containing concentrations of enemy troops in forward areas behind the enemy lines, under conditions when visual attack by fighter-bombers was impossible. Although bombs dropped with this accuracy were of some effect, it in no way replaced the value of bombing by fighter-bombers under good visual conditions, when an accuracy possibly as good as 20 yards was obtained. Since the bombs dropped by fighter-bombers were of relatively small size, the value of their bombing depended to a great extent on a high degree of accuracy which was possible only when the bombing was visual, and was rarely achieved even then.
Richard Hough of 197 Squadron in 'One Boy's War', described being controlled by an MRCP while bombing with his Bombphoon;
"Some scientist, who became very unpopular with us, had invented a form of blind bombing, straight and level, by radar. We felt very foolish flying in loose formation above 10/10th cloud and in blazing sun all pressing the bomb tit together when a distant voice over the R/T ordered us to do so. We were told the bombing was highly accurate. 'If we're going to have a wizard prang, I like to see it,' someone complained."
The effective range of the Type 25 Convoy was increased with the introduction of the American Microwave Early Warning Set (AMES) Type 70 Radar to 83 Group at Erp in Holland in early February 1945. A second Type 70 was built for 84 Group but was not operational at the end of hostilities.

Re: Bomber Command failure at Urft Dam.
 

For those interested, here are contemporary photos of the Urft and Schwammanauel dams together with a map of their location.
Tony

Re: Bomber Command failure at Urft Dam.
 

Hi Tony,

You have not included one of the more obvious possibilities - simply, that the winter weather, which severely restricted bombing by the Allies in December 1944 and January 1945, is a likely explanation for the lack of bombs dropped on the dams. No air force is in the habit of expending a large effort to send a force of bombers to the target only not to bomb unless there are very good reasons.

I would suggest that you find and read the relevant RAF BC Group reports and RAF BC Group and Squadron Operational Record Books in AIR 14 at TNA in order to establish the reasons you seek (8 Group would be a good place to start). The other reasons you have stated are conjecture (unless you find memos from Harris or other BC Commanders directly supporting your hypothesis). Another Bomber Command file worthy of checking is AIR 14/1436, which specifically concerns operations against the Roer and Urft River Dams in the period between October-December 1944.

As to a pinpoint attack by 617 and 9 Squadrons (which were part of Cochrane's 5 Group) with Tallboys; besides any target and resource allocation issues decided at a higher level, reasonably good visibility and other factors such as wind speeds within accepted parameters would be needed in the target area at normal operational height in order to visually bomb the dams using the SABS bomb sight, which, I might add, was a complicated piece of machinery that required a very well-trained and skilled crew to operate with any accuracy, and a long run in to the target before release. Reading the 617 ORB entries in the link provided earlier in this thread bares these points out, and it is obvious from the ORBs that the crews tried repeatedly in well less than ideal conditions to conduct successful bomb runs.

The Tallboy Lancasters could not be equipped with H2S and, anyway, I doubt that any existing blind bombing aid in use at that time could guarrantee the level of accuracy required for the Tallboys to be effective against the dams (i.e. to justify the expenditure of such a valuable commodity as a Tallboy - this is conjucture, further checking of RAF BC files would be needed to exactly establish any Tallboy targeting criteria). It would seem highly unlikely that conventional bombs would have done anything more than pockmark the dams.

Cheers

RodM

Re: Bomber Command failure at Urft Dam.
 

Hi Rod,

You are quite right. I did not originally include the possibility that weather could have explained the RAF failure at the Urft Dam, for the reasons given; the existence of H2S, Oboe, GEE-H and the blind bombing experiments undertaken by 2TAF (admittedly two months later in February/March 1945). I assumed that by December 1944, BC could operate in 10/10th cloud at least within Oboe range. I now know differently.

But it remains difficult to believe that BC should have accepted a bombsight like SABS requiring a long visual run. The adoption of the Norden bombsight by the USAAF could be explained by their clear US skies; they were certainly shocked by European conditions when they eventually arrived. The gales over Lincolnshire referred to in the 617 ORB were another matter since they made take-off by fully laden bombers hazardous.
I t is now known that weather stymied 617 and 9 Squadrons' attacks on the Roer dams. That is a fact, and my thanks to those who provided the evidence.
I will also look at the references in TNA that you have kindly provided.

I came at this matter through the pages of Courtney Hodge's diary, in which he recorded doubts that BC had bombed based on the lack of results. Hodges was GOC 1 US Army, and since air-ground cooperation was organised at army level, he would have been fully briefed by BC. During the time of the bombing, his troops were a maximum 3 miles from the dams.

The question of sabotage by Harris cannot be dismissed as unobvious. It was strongly suspected at the time by Portal. On November 1, 1944 Harris wrote to Portal; “In the past eighteen months, BC has virtually destroyed forty-five of the sixty leading German cities....Are we going to abandon this vast task?” Portal replied; “I have, I must confess, wondered at times whether the magnetism of the remaining German cities has not in the past tended as much to deflect our bombers from their primary objects (transportation, oil, dams) as the tactical or weather difficulties (in attacking oil refineries) which you describe”. You will recall that Harris was told he could fall back onto city bombing whenever weather made the primary targets impracticable. So Harris had a vested interest in calling the weather bad. Harris never hesitated in ordering city raids. “I was against putting everything into oil. It was using a sledgehammer to crack a nut”. He threatened to resign, and Portal gave in, at least to the extent of listing as targets, Berlin, Dresden, and Chemnitz, which sealed Dresden's fate.
So you had Harris advocating city destruction, Portal advocating oil attacks, and Sinclair wanting troop support such as the Roer dam destruction. So my question whether internal Air Ministry feuding had anything to do with the failure at the Urft Dam was, I hope you will agree, not far-fetched, even if it turned out to be a non-starter.

Tony

Re: Bomber Command failure at Urft Dam.
 

post #3

Re: Bomber Command failure at Urft Dam.
 

Yes, Hodges mentioned bad weather.
BC reported bombing in spite of bad weather but without results.
H2S, Oboe, GEE-H and radar-control are weather independent.
At that point in the thread it had not been established that BC's technique for dam destruction required a long clear run-up. That came up later.
And even now the thread has not established that even in clear weather, and with a direct hit, BC could destroy a high-walled or concrete-filled earth dam since they had abandoned the proven (for high-walled dams) bouncing bomb and focused on Tallboys.
I suspect they needed Grand Slam to breach the Schwammenauel.

Tony

Re: Bomber Command failure at Urft Dam.
 

"But it remains difficult to believe that BC should have accepted a bombsight like SABS requiring a long visual run. "

You could perhaps explain the operation of any alternative? The design and creation of any bombsight is a specialised task, the SABS was the best available at the time. Precision targeting is a difficult task, there were no lasers or GPS in 1944. One of the prime requirements is that the aircraft be absolutely steady and dead on the right course, and this is not an instantaneous achievement.

Re: Bomber Command failure at Urft Dam.
 

Graham.
Let's define the required accuracy.

"Tallboy and Grand Slam required to be dropped within 150 yards of the target from 20,000 ft.
617 Sqn with SABS achieved 170 yards over the period June-August 1944, improving to 125 yards in February-March 1945."
source: http://www.geocities.com/skidaddy20000/Air-Bomber.html

"Oboe was extremely accurate, with an error radius of about 110 meters (120 yards) at a range of 400 kilometers (250 miles), about as good as optical bombsights."
source: http://en.wikipedia.org/wiki/Oboe_%28navigation%29

I understand that Oboe was not a bombsight. The effect of wind and speed and length of drop would have to be computed separately, but was well within the technical capabilities of the time (SABS and Norden).

Furthermore by December 1944 there would have been time to set up Oboe cat and mouse sites in Holland and France to extend Oboe coverage well beyond Berlin at 20,000 ft.
It is not clear whether in December 1944, 617 Sqn had achieved the required accuracy.

Tony

Re: Bomber Command failure at Urft Dam.
 

It should be noted that all these bomb sights require accurate knowledge of the winds at all levels through which the bomb is to drop. Our met people simply did not have the means, I know special flights were made to determine target area winds, but for the accuracy required and the drop height, too much data was necessary.
Also visibility of the target, NW Europe winter weather does not help much.

Re: Bomber Command failure at Urft Dam.
 

My comment was restricted to your slur on Bomber Command for operating the best bombsight available at the time.

However, you have now added " by December 1944 there would have been time to set up Oboe cat and mouse sites in Holland and France to extend Oboe coverage well beyond Berlin at 20,000 ft."

Really? Perhaps they had, I don't know. But what were the requirements for setting up such stations? What were the needs/requirements for such stations, to be balanced against all the other priorities for getting military equipment into Western Europe in those few short - and event-filled - months? Was it quite the easy. open-and-shut case that you present?

I think you meant Belgium and France - we hadn't actually got very far into Holland, and the Germans were still blocking the direct supply routes.

Re: Bomber Command failure at Urft Dam.
 

Graham.

Why the word 'slur'?

Did you read the following in the website I quoted? Note especially the comment about tactical freedom, which was obviously missing when 617 Squadron tried to bomb the Urft Dam but could not find enough clear sky to establish the required length of SABS bomb run, and so failed the mission.
The RAF were obviously concerned about the best (SABS) being the enemy of the good (MkXIV/T1.

"Two other precision bombing squadrons were formed based upon the Mk XlV bombsight, and in the period of February to March 1945 their average error was 195 yards. It is not surprising that when the Norden was offered to the RAF later in the war it was rejected.

Less than 1,000 SABS bombsights were manufactured and after the war great difficulty was experienced in finding sufficient sights to equip two Lincoln squadrons for precision bombing against Japan. Compare this with the 23,000 T1 sights manufactured in America.

There was in Bomber Command at the time much discussion on the comparative merits of the two bombsights. The SABS, although potentially more accurate, lacked the degree of tactical freedom afforded by the Mk XlV/T1. As a result the Mk XlV/T1 was known to Bomber Command as the ‘area’ bombsight of the RAF and the SABS as the ‘precision sight.’

It was a much more complex sight to use and to maintain than the Mk XlV/T1 and required more man-hours in manufacture. For the majority of the squadrons in Bomber Command the Mk XlV/T1 was still the preferred sight."
source: http://www.geocities.com/skidaddy20000/Air-Bomber.html

And I did mean Holland, where 2TAF were experimenting with MRCP and radar controlled bombing at Erp. 2TAF and BC were in the same organization fighting on the same side, but that didn't mean they necessarily spoke to each other.

As for your question about Oboe, I do not know the answer. The RAF had another, and similar system, called GEE-H, which became standard post-war, AFAIK.
The RAF was at the cutting-edge of navigation and bombsight technology. Hence my continued surprise that the cutting-edge 617 Squadron should have been stymied by 10/10th cloud in December 1944. But that's no more than a statement about my ignorance, which has been considerably lessened by this discussion, for which many thanks.

Tony

Re: Bomber Command failure at Urft Dam.
 

"But it remains difficult to believe that BC should have accepted a bombsight like SABS requiring a long visual run. "

If not a downright slur, that's at best an over-critical attitude. It is only "difficult to believe" given the known presence of something superior, which did not actually exist.

Re: Bomber Command failure at Urft Dam.
 

Hi Tony,

I think the crux of the question is establishing what force, applied with what accuracy was required to breach the dams sufficiently in order to achieve the desired outcome of draining them enough to reduce or eliminate the threat to the US 9th Army.

The Tallboy, while seeming to be a powerful weapon, still required delivery to a very high degree of accuracy to be effective because it was a single munition. SABS was the only means, as far as I am aware, that was available at the time to drop the Tallboys and Grand Slams with such a high degree of accuracy. If the 617 Squadron ORB is studied with regard to the raids to breach these dams, two things stand out to me - (1) the bombing with Tallboys was carried out from an unusually (I think) low height, probably due to the restrictions imposed by the cloud and weather, and (2) from the crew reports it appears that some Tallboys may have landed as close as '50 yards' from the dams, without causing the desired breach. These two points are salient because lowering the bombing height would have reduced the effectiveness of the munition (although also potentially increasing the accuracy of delivery) and it would appear that close to a direct hit would have been required the breach the dams.

If you ever see the low angle photo of the results of the first Grand Slam attack against the Bielefeld viaduct on 14 March 1945, it is interesting to see the Tallboy bomb craters very close to the viaduct that were not enough to cause the collapse of the viaduct. The Gland Slam was a direct hit.

The SABS sight, as mentioned, was a very complicated computational bomb sight, so that, besides the need for very accurate flying, a series of measured parameters had to be programmed into the sight before bomb release (and this is where the entire crew of the Lancaster could be involved in the process), and the SABS had to be visually centred on the target. If any one of the measured parameters was inaccurate or changed before bomb release, or if the visual centring of the sight was disturbed, then the bomb could fall wide of the intended aiming point. This fact still holds true today, in spite of much more advanced computational sights, and it has only been the introduction of self course-correcting munitions that has improved single munition accuracy (and, if I remember correctly from various US governmental reports after the first Gulf War, even laser-guided munitions that required visual painting of the target could be disturbed by cloud).

OBOE et al would not, IMHO, have been accurate enough to use for the delivery of Tallboys, and, besides, OBOE can only produce a theoretical bomb release point that probably could not account for all of the variables required for accurate delivery of the Tallboys; many of these variables having to be measured and established in real time during the bomb run.

'Area' raids of any kind (and by this I mean the dropping of a large number of munitions over a given area) have an increased probability of hits provided that the area being saturated includes the intended target. With regards to the dams, I think it probable that while an area attack could have resulted in more hits on the dams themselves, the munitions used would not have been powerful enough the sufficiently breach the dams.

I also think it important to remember that had there had been one clear enough day during that period in December 1944 or at least one 'lucky' hit, the results of the Tallboy attacks against the dams could have been much different (assuming that a direct hit would cause the necessary drainage). Much published literature points to the operational successes of Tallboy, without fully balancing this against the operational failures. I, for one, would be interested to see statistics indicating the average number of Tallboys dropped for each target hit (including those dropped when the target was not hit).

For me, two unanswered questions come out of this discussion - (1) why were no more attempts made after December 1944 to breach the dams (bearing in mind that the weather in January 1945 was similar to December 1944)? (2) why was the plan for the ground campaign not modified in view of the known risk the still active dams posed to its successful execution?

Cheers

Rod

Re: Bomber Command failure at Urft Dam.
 

Quite right. The effort expended matched the direct guidance (instructions) from Eisenhower, the Supreme Commander, up to the point that the weather prevented operations with current technology. The dilution of the bombing offensive against Germany was not popular with Harris, but the squadrons flew every possible mission in all theatres, including the unpopular ones. Discussions about bombsights never stopped a mission from being mounted, but weather did. A high profile failure to complete an assignment that was technically feasible would not have helped Harris in any way in his dealings with Eisenhower or Churchill, and it has been competently demonstrated that there was no reasonable expectation of success for the destruction of the Urft Dam using the weapons available. Who knows what would have happened if other weapons or technology had been accesable, but obviously they weren’t.

Bruce

Re: Bomber Command failure at Urft Dam.
 

Rod,
A timeline might provide some kind of answer to your two questions (why BC attempts stopped, and why the ground campaign was not modified).
September 25, Market Garden failed and 21 Army Group was ordered to concentrate on clearing the Scheldt. Since they had Groesbeek, they began to plan Op Gatwick, an attack through the Reichswald to Wesel (became Op Veritable).
September 25, 1 US Army (Hodges) was told to reduce the salient on the west bank of the Maas (he failed), and to drive to the Rhine between Dusseldorf and Bonn through the Aachen gap.
October 2, Aachen attacked instead of bypassed. Huertgenwald entered.
November 3, Schmidt taken, only 2 miles from Schwammanauel Dam.
November 7, major attack towards the Roer.
November 11, Hodges first realised the significance of the Roer dams, when a German map was captured showing the flooding consequent to dam destruction. If Hodges had realised the significance earlier, he might have taken the dams by attacking up the Monschau corridor on October 2, instead of entering the Huertgenwald (where his forces were bled white with 24,000 casualties and 9,000 cases of trenchfoot and battle exhaustion). But instead of taking the dams after November 11, Hodges asked for their destruction by the strategic bomber forces, which Ike ordered. “After several bomber strikes failed to destroy the dams, however, all air effort ceased, much to the disappointment of Hodges who continued to advocate air action in his unshaken belief that a 1,000-plane raid could do the job”.
December 10, Hodges ordered the dams taken.
December 16, Ardennes offensive intervened.
February 5, Hodges ordered the dams taken in support of IX USArmy's attack across the Roer in Op Grenade scheduled for February 9. 375,000 US troops waited to cross the Roer in a pincer movement coordinated with 21 Army Group's Op Veritable, scheduled for February 8.
February 5, little progress by Hodges' troops towards the Schwammanauel Dam.
February 6, at 1800 hrs an engineer company broke through and raced for the dam. They arrived at midnight to find the valves destroyed in the open position to release a continuous flow until the reservoir was emptied over several days. Why US engineers did not then blow the dam is unknown, and I have not seen the question asked. “First Army's neglect in seizing the dams was only eclipsed by the casual admission by Hodges that he never really expected success anyway. Kay Summersby – Ike's driver and mistress - noted that “E always thought this would happen”.
February 8, Veritable opened.
February 13, Roer peaked at 11 feet.
February 15, Roer began to subside.
February 21, Simpson decided to cross on February 23.
February 23, first boat across at 0330hrs, 3 footbridges destroyed before one survived at noon, treadway bridge completed at 2000hrs but destroyed by German aircraft at 2015hrs.
February 24, first treadway in use at 1100hrs. Attacks made by 97 LW sorties including Me262 (presumably KG54, and their first sorties?) and four fighters with US markings assumed to have been operated by the LW.
Quotations are from the Whitakers' book, Rhineland.

Tony

Re: Bomber Command failure at Urft Dam.
 

Rod,

A specific answer to your first question is given in Ellis' Victory in the West, Vol II, page 164; "On the 12th of December SHAEF stopped the bombing because it was diverting too much effort from strategic targets".

Ellis also says that SHAEF "hoped that BC would be able to repeat its success against the earth dykes of Walcheren".

This success occurred on October 3, when 259 Lancasters and Mosquitos aimed 1,270 tons of HE on the dike at Westkapelle. When a 100-yard breach was observed with the sea pouring through, the Master of Ceremonies ordered ten Lancasters carrying Tallboys to return to base without releasing their bombs.

Cheers, Tony

Re: Bomber Command failure at Urft Dam.
 

Just a couple of comments regarding the previous posts. 617 Squadron Lancasters that carried tallboys could not be equipped with H2S. I have correspondence from Harris, Cochrane, Bennett, Saunby and others discussing this and also equipping Lancasters with Oboe, which also could not be fitted on a Lancaster with H2S.
While Oboe equipped aircraft could drop bombs or target indicators with the same accuracy in any type of cloud (the Oboe crews never used any visual references on a bombing run), the main force aircraft bombing the Oboe TIs were greatly affected by cloud. Sky marking was much less accurrate than groundmarking and the winter season Oboe attacks were on the whole less successful due to the weather.
Mobile Oboe transmitters certainly extended the range and allowed Oboe operations to eventually hit Berlin but the extended range did not translate into lower operating heights for the Oboe crews unless they were leading formations of aircraft. Typically Oboe Mosquitoes operated from 28,000 to 34,000 feet. Even with close targets in the Pas de Calais, when sometimes their bombing runs began over the Thames estuary they generally operated over 20,000 feet. Height gave them protection as well as range and they were still able to maintain their accuracy. One example was the D-Day attack at Pointe du Hoc just a few hours before the Americans came ashore. 3 Oboe Mosquitoes marked for 114 Lancasters, 1 from 30,000 feet, the other 2 from 18,000. The Mosquito at 30,000 had a target error of 70 yds., the 2 at 18,000 had target errors of 140 yds. and 220 yds.
Dave Wallace

Re: Bomber Command failure at Urft Dam.
 

Although this thread seems dormant it has been most interesting reading particularly since my father was the sole survivor of LM637 LE-V shot down over the Urft Target area 8th December '44.
A few years ago I visited the area to get some background and context to the raids on the Urft. Adverts were placed in the local newspapers asking for information and we were put in touch with local historians and the water company who manage the dam gave us a guided tour of the inner passages in the dam.

According to the water company engineers, who recently have blasted further inspection galleries, it would have been impossible to destroy because the rocks used in construction were so tough, it gave them big problems in driving the extra galleries.

I have put together a storyboard with some interesting photos of the dam and nearby craters

https://www.facebook.com/media/set/?...3&l=eb5f4ee42d

Re: Bomber Command failure at Urft Dam.
 

Hi Tony,

There is a pile of correspondence on these dams between Bert Harris, Portal and SHAEF in the Harris archive. I recall seeing them when I was doing some work for the BCM.

Kind Regards

Andy Bird

Re: Bomber Command failure at Urft Dam.
 

Tony,

Re: Bomber Command failure at Urft Dam.
 

Hi all.

Allthough this tread has been dormant for some time, here is the explanation of what went wrong with the attacks on these dams. From AIR 24/206 (Bomber Command ORB – Operations Branch January 1944 – May 1945).

During the period October – December, 1944, serious consideration was being given to the destruction of two RUHR River Dams (URFT and SCHWAMMENAUEL) in support of the Army advance on RHINE. Both Dams were belived to have been mined by the Germans with a view to their destruction at such time as might be tactically suited to the German Forces operating to the West of those Dams. The project was first passed to this Command on the 25th October, 1944, for information only. All available target material and the latest P.R.U. photographs were collected, however, and passed to No. 5 Group for study. On the 6th November, 1944, further details of the Dams were recived from Bomber Command Advanced confirming that 9th Air Force had been informed by S.H.A.E.F. that the water in the Dams was too low to admit of successful attacks and that they would not be attacked by this Command unless changed conditions warranted it. On the 29th November, 1944, a request was recived from S.H.A.E.F. through Bomber Command Advanced for an attack on the RUHR Dams as soon as the weather permitted. The decision as to which or both of the Dams would be attacked rested with this Command. Replying by signal on the 30th November, 1944, this Headquarter stated that the position of the front line troops prohibited a blind attack by G-H, but that a visual attack on both Dams would be undertaken by the first opportunity. A new bomb line was recived from the 9th Air Force on the same date, however, and it was found that the troops were further away from the target than had been thought and a blinf G-H attack by No. 3 Group was therefore planned for the 1st December, 1944. This attack was cancelled owing to weather conditions at 0730 hours on that date. The two Dams at that time under consideration were the URFT (No. 1 Dam) and the SCHWAMMENAUEL (No. 2 Dam). Between the 1st and 10th December, 1944, no less than 13 operations were laid on against these Dams involving a total of 1656 aircraft, 1476 aircraft on the URFT and 180 aircraft on the SCHWAMMENAUEL Dam. Of this total, 800 aircraft were cancelled before take-off; 856 were cancelled or went to the target and brought back their bombs pwing to adverse weather conditions. Only 152 aircraft dropped their bombs.
The plan of attack against both Dams was a low level attack first with samll bombs to peel off the air face of the Dam, followed by a low level TALLBOY attack also against their face. At that time, it was considered that an attack on No. 2 Dam (SCHWAMMENAUEL) was unlikely to be very effective owing to the low level of the water. Following the unsuccessful attemptss indicated above, consideration was given to an attack against the URFT Dam using the UPKEEP weapon, but for various reasons this was not considered practicable. At Encl. 67A is a personal signal from the C-in-C to A.V.M Orland at Bomber Command Advanced which states that it was apparent that the URFT Dam could not be broken by bombing and that there was not sufficient soace to allow for the use of UPKEEP. It was hoped, however, by bombing the spillway to break the lip and masonery floor with the object of using the overflow to erode the hillside. The C-in-C pointed out that this would only be practicable if the hill was composed of earth and boulders and not rock. He considered that if the operation was successful, it would be possible to lower the water level in the Dam to below the point where it remainded a threat. Provided the enemy did not become aware of the intention and use sluices, he hoped that the released water might fill the bottom Dam (SCHWAMMENAUEL) sufficiently to make it vulnerable to bombing. He therefor started his intention of continuing to attack the URFT Dam until the trial had proved that the hillside was solid rock and would not erode. He pointed out that should the enemy use the sluices to keep the water below damage level, there was no hope of success. Between the 11th and the 13th December, 1944, three further attacks were laid on, but two were cancelled owing to weather and of the 684 aircraft detailed for the 11th December, 1944, only 183 attacked. At the Air Commander’s Conference at S.H.A.E.F. on 15th December, 1944, the Deputy Supreme Commander requested that no further attacks be made on the Dam.


All the best,
Bengt