Dambusters debated.-

Was the legendary and courageous 1943 RAF Dambusters Raid a ‘strategic success or a conjuring trick’? PAUL STODDART from the Royal Aeronautical Society Air Power Group provides a report on an academic debate on the effectiveness of Operation CHASTISE.


Seventy years have elapsed since 617 Squadron led by Wing Commander Guy Gibson breached the Mohne and Eder dams in western Germany on the night of 16-17May 1943. Despite the passage of time, the release of previously classified information and the intensive study by historians, opinion remains divided as to the effectiveness of the operation. To commemorate what remains one of the most, if not the most famous single air power action, on 4 April the Cranwell branch of the RAeS devoted its annual Trenchard Lecture to a debate on Operation Chastise.

The three speakers were the distinguished historians and authors Professor Eric Grove, Dr Peter Caddick-Adams and James Holland. The debate was hosted by the Royal Air Force College Cranwell and took place in the splendid setting of College Hall Officers’ Mess with an audience of around 80. Cranwell is a few minutes flying time south of RAF Scampton from which 617 Squadron flew on the Dams Raid.

The Admiralty and the RAF carried out extensive tests at sites around the country. These revealed that the drum-shaped bomb (codenamed 'Upkeep') needed to be dropped from a height of 60 feet (18m), and at a ground speed of 232mph.

The bomb would spin backwards across the surface of the water before reaching the dam. Its residual spin would then drive the bomb down the wall of the dam before exploding at its base.

All that was needed now was men to fly specially modified Lancaster bombers which would carry the 'Upkeep'.

Divided Opinions.-

The official history: “…the most precise bombing attack ever delivered and a feat of arms which has never been excelled”. “…the effects of this brilliant achievement upon the German war machine were not, in themselves, of fundamental importance nor even seriously damaging”.

“The truth about the Dams Raid is that it was a conjuring trick, virtually devoid of military significance…The story of the raid is one of sloppy planning, narrow-minded enthusiasm and misdirected courage”.

The most widely read account of the RAF’s contribution to the strategic air offensive against Nazi Germany is probably Max Hastings’ ‘Bomber Command’. Of the 425 pages, barely a page is actually assigned to the Dams Raid and Hastings sums up the operation as follows: “The Ministry of Economic Warfare in London correctly judged that the Mohne and the Sorpe dams were central to the Ruhr water supplies. But after destroying the Mohne, 617 Squadron used their remaining mines to wreck theEder dam, which was quite irrelevant. Bomber Command had merely judged it more easily breachable…than the Sorpe”.

“Operation CHASTISE achieved considerably more than it has been given credit for, particularly by latter-day historians. The Dambusters Raid was a legendary feat and a remarkable strategic success; its undoubted accomplishments do not deserve to be belittled unjustly”.

The ever quotable Sir Arthur ‘Bomber’ Harris offered this assessment of the Upkeep mine: “It was…designed…outside the…Air Ministry; it [was] almost a rule that such weapons were successful, while those produced by the official organisation were too often failures”.

Map showing the route of the raid.

The Debate – Opening Statements – Opening Salvoes.-

Dr Peter Caddick-Adams.

The debate opened with each speaker offering an initial statement on the operation’s aims and effectiveness. Dr Caddick-Adams began by asking the rhetorical question as to how success should be defined so that the operation could be objectively assessed. He emphasised that much of the general understanding of the raid is based on the media’s 1943 presentation of the results, i.e. a less than impartial view. In early 1943, though the Allies had defeated the Axis in North Africa, the Eastern Front was still undecided. American forces were building up in the UK representing a growing challenge Britain’s leadership role in the West. It was therefore understandable that the headlines were very positive and the accounts offered an exaggerated assessment of the results achieved. Dr Caddick-Adams emphasised that the raid should not be considered in isolation but in the context of Bomber Command’s Battle of the Ruhr. That campaign ran from March to July 1943and involved 43 raids and around 18,000 sorties in which 872 aircraft were lost. That was a rate of 4.8% i.e. above the usually accepted limit of 4%; when damaged aircraft were included the casualty rate was 11%. The aim of the five month campaign was to neutralise the German war economy yet arms manufacturing was already widely dispersed. The London based Ministry of Economic Warfare (MEW) questioned the focus on the Ruhr pointing out that, for example, the region contained only one aircraft factory. In short, the Ruhr while important was not the sole target worthy of attention.

James Holland.

James Holland opened by referring to the book on the raid that preceded his own. John Sweetman’s ‘The Dambusters Raid’ was originally (sub) titled ‘Epic or Myth’, a comment on the stark contrast between the various schools of thought. He noted that using Google image search for Guy Gibson produced as many photos of the actor Richard Todd who portrayed him in the film. Similarly, the film is often the entirety of people’s knowledge of the operation. The film portrays a hard pressed wartime Britain that still has real clout and the nation can be proud of the achievement. It also presents Barnes Wallis (through Michael Redgrave’s portrayal) as a detached academic rather than the very effective networker Wallis actually was. Another misrepresentation is that of Wallis single-handedly promoting his dams attack scheme in the face of reactionary opposition from the Air Ministry. He was a friend of Group Captain Winterbottom who worked in RAF Intelligence and who was extremely well connected with influential officials. Additionally, the Air Ministry had, in 1937, identified the importance of the Ruhr dams but had also noted the difficulty of breaching them. To some extent Wallis was pushing on an unlocked door and the scepticism he faced from certain quarters was not unjustified given the challenge of using Upkeep successfully. For example, the commander-in chief of Bomber Command, Air Chief Marshal Harris had taken over a year to build up the force for his area bombing campaign. He viewed low level attacks (as required for Upkeep) as being unacceptably dangerous and with insufficient prospects of achieving the significant results claimed by the ‘panacea merchants’ promoting them. Harris objected to the conversion of up to 30 Lancasters for Upkeep and advocated to the Chief of the Air Staff (CAS), Sir Charles Portal, against this. To his credit, when Portal authorised Operation Chastise, Harris did all he could to ensure its success.

Professor Eric Grove.

Professor Grove emphasised that the aim was to inflict decisive damage on the ‘white coal’ of the Ruhr; the dams provided hydro-electric power, water for steel making (each ton of steel required eight tons of water) and drinking water for a very densely populated region. The British had studied the region and the MEW had correctly identified the central importance of the Mohne and the Sorpe dams to the Ruhr. The Upkeep mine was specifically designed to attack masonry built gravity dams such as the Mohne while the Sorpe was of earth buttress design and so was far less vulnerable. Nevertheless, Wallis believed that several Upkeeps dropped on the crest of the Sorpe; the aim being to crack the concrete core causing leakage and eventual breaching or forcing the reservoir to be drained to enable repair. Relatively little effort was expanded in determining how best to attack the Sorpe and in the course of planning, the operation developed to exploit the weapon rather than to achieve the overall aim, i.e. to disrupt theRuhr’s industry. Thus the raid focus was the Mohne and theEderdams with the Sorpe as an afterthought. (It should be noted that while the Eder was a gravity dam and so vulnerable to Upkeep, it was not in the Ruhr valley. It held back the then largest reservoir in Europe). Had the Mohne and Sorpe been breached, the resulting effects would have been much greater.

Of the five aircraft allocated to the Sorpe, only one reached the target; it bombed accurately damaging the dam crest. The main force of nine aircraft expended five mines on the Mohne and the remaining four on the Eder. Of the reserve wave of five aircraft, three were directed to the Sorpe and two to less important dams in the Ruhr Valley. Of the Sorpe ‘three’, one never reached the target, one hit the dam causing further damage and the third could not locate the Sorpe in the thickening mists of the early morning. Of the other two aircraft, one was lost and one attacked the Bever Dam (instead of the intended target, the Ennepe Dam) but caused no damage.

The Möhne dam in Germany's Ruhr valley secured the water supply for much of the surrounding area. Water from its reservoir was also used to generate electricity.

Professor Grove stressed that he was not denigrating the value of the operation though the loss of eight aircraft from nineteen (42% and 53of 56 crew killed) was very heavy. If applying the crude measure of people killed, the raid might be deemed effective. Sixty eight people were killed per aircraft committed and 162 per aircraft lost; the figure for a conventional raid on Dortmund was one tenth of the latter measure. In the still controversial February 1945 attack on Dresden, 37 people were killed per aircraft committed.

Operation Chastise did not knock out the Ruhr but it was a significant addition to Bomber Command’s most productive campaign. Professor Grove agreed with the conclusion of a recent, notable history of Germany’s wartime economy specifically that the Ruhr campaign was a great success and “stopped Albert Speer’s expansion plan in its tracks”. During June and July 1943, the Ruhr’s output fell. Harris had been right; the Dams Raid did not achieve all that had been hoped (and claimed) for it but it was still effective. It was also very good for British prestige in Washington (and Moscow) “eating the 8^th Air Force’s sandwiches” by showing that the RAF could also achieve precision bombing as well as conducting area bombing.

Professor Grove summed up his introduction by likening Operation Chastise to the Battle of Trafalgar. The significance of Trafalgar could be argued on the grounds that the war against Napoleonic France continued for a further ten years. Yet Trafalgar was “an important outward sign of inward grace” in that it demonstrated the Royal Navy’s capability and professionalism. Likewise, the Dams Raid did so for the RAF.

The Wider Debate.-

James Holland pointed out that prior to the operation, there were differences in opinion as to what it was likely to achieve – even among the supporters. In fact, Wallis was one of the few (perhaps the only person) who believed that breaching the dams would result in cataclysmic effects that would substantially shorten the war. He was convinced that cutting off the power to the Ruhr would cause production to practically cease. However, others had less ambitious expectations for Upkeep’s capability and hence the raid was planned around the weapon. That is, its suitability for gravity dams was an important factor notwithstanding the importance of the Sorpe Dam.

The debriefing of Wing Commander Guy Gibson's crew at Scampton after the raid. Of the 133 aircrew that took part, 53 men were killed and three became prisoners of war. On the ground, almost 1,300 people were killed in the resulting flooding.

The operation was actually more successful than some commentators have claimed even though it was achieved less than the 1955 film implied. (The Hardest Victory: Eleven factories were destroyed and 114 damaged. 2822 hectares farmland were ruined with 6316 farm animals killed. Twenty five road bridges were destroyed, with ten damaged. Various power stations, pumping stations, water and gas facilities were put out of action with serious disruption to water, electricity and gas supplies). To some extent, the criticism of the last 30 years or so has been a reaction to the original overstatements. The rebuilding of the Mohne and Eder was achieved remarkably rapidly (around five months – building the Mohne took five years) and the fact that considerable effort was devoted to this is proof of Chastise’s success. Although there was no immediate water shortage in the Ruhr, it was necessary to rebuild the dams quickly in order to collect the winter rains and so provide water in 1944. The dams were also iconic structures for the German population; examples of Teutonic achievement. Breaching them was an affront that demanded a prompt response. Rebuilding diverted considerable effort from other projects (48 hours after the raid, 7000 workers were heading for clear-up and rebuilding work in the Mohne valley, the Eder valley,Dortmund and Kassell. Another 20,000 were also assigned to various repair tasks with many diverted from the building of the Atlantic Wall). James Holland concluded by emphasising that all wartime commanders and planners seek major damage from relatively small effort; despite 617’s losses, the Dams Raid was one of the rare cases to actually achieve this.

Peter Caddick-Adams offered three points. Firstly, he referred to one of the principles from Sun Tsu’s ‘The Art of War’ – to avoid costly attritional conflict but instead ‘fight smart’ and strike your opponent so as to cause major loss at comparatively low cost. In this respect, Operation Chastise was successful. Admittedly the headlines and newsreels of the day included some wishful thinking and certainly the Third Reich was not in danger of collapse owing to the damage caused. However, Britain was engaged in a titanic contest and the maintenance of national morale was extremely important so making some overstatement understandable in the circumstances.

Secondly, the raid must be seen in the wider context of WW2 as a whole and 1943 in particular. In early 1943, the Allied leaders met at the Casablanca Conference to decide their strategy for defeating the Axis powers. There was much debate as to how best to engage Nazi Germany with the Americans advocating a landing in France during 1943. Churchill believed that to be excessively risky and he succeeded in postponing the invasion to the following year. However, this option depended on the expansion of the strategic bombing offensive and an increase in its effectiveness. The UK-US relationship was that of an ad hoc coalition; the two nations had common interests but there was also competition between them. The American view was that the RAF’s area bombing policy was less effective than the 8^th Air Force’s daylight campaign. Chastise was an example of British ingenuity (to both the US and the Soviet Union) and of the ability to achieve precision and significant effect in a night attack.

Thirdly, it is worthwhile examining the Dams Raid from the perspective of effects-based operations (EBO) and Clausewitz’s theory of the centre of gravity (CoG), i.e. an indispensable capability. The principles of EBO include seeking actions likely to achieve significant, beneficial results. While that may seem obvious, military history offers many examples where actions were taken because they were could be taken rather than because they were the best option. An adversary’s CoG is the essential component of their ability to fight. Wallis believed that power generation was the CoG of Germany’s war making capacity and that breaching the dams would neutralise it – a war winning result. This was an unrealistic view given the resilience of the German economy but it is also a slur to describe the raid as a ‘conjuring trick’ – the operation caused significant damage.

From 9.28pm on 16 May, 133 aircrew in 19 Lancasters took off in three waves to bomb the dams.
Gibson was flying in the first wave and his aircraft was first to attack the Möhne at 12.28am, but five aircraft had to drop their bombs before it was breached.
The remaining aircraft still to drop their bombs then attacked the Eder, which finally collapsed at 1.52am. Meanwhile, aircraft from the two other waves bombed the Sorpe but it remained intact.

Following the general consensus between the speakers there was than a difference in views between James Holland and Professor Grove. The former proposed that some ‘mission creep’ occurred with the RAF going beyond the initial aim of damaging the German war economy. Effects beyond the economic were considered worthwhile hence the focus on the Eder Dam after the Mohne was breached. Destroying two iconic structures had very significant psychological effect. The gravity design Eder Dam was not only vulnerable to Upkeep but it also held the largest reservoir in Germany. Professor Grove strongly disagreed. He emphasised that the whole logic of the raid was to inflict industrial damage and to maximise that it was essential to breach both the Mohne and the Sorpe. (See the section: The background to operation Chastise) As this was not achieved, the operation could be judged to have failed on the basis of its original aims. However, he expressed his respect for the achievement of the crews and noted that the raid was cost effective in terms of the results despite the heavy losses. It achieved a great deal but suffered from being developed in great haste (James Holland concurred) and subsequently achieved both less than what was intended and what might actually have been possible.

Dr Caddick-Adams noted the importance of raising the morale of both the British population but also that of Bomber Command which, at that time, was fighting the Battle of the Ruhr. Operation Chastise achieved these aims. It was timely as the Command had just completed a series of thirteen attacks on the U-Boat pens on the French Atlantic coast; many aircraft were lost and not one pen was destroyed. (Professor Grove interjected here pointing out that the RAF waited until these massive structures had been completed before attacking them).

James Holland agreed with the value of maintaining the morale of the hard pressed bomber crews. The achievement of spectacular results was important and that was a factor in selecting targets on the basis of weapon suitability and hence likely effectiveness. In short, selecting the Eder made sense. The Ministry of Economic Warfare was correct in identifying the importance of the Sorpe but it was focused on the industrial level and not the wider issues such as morale and national influence. (Note: 27 Mar 43: A Chief of the Air Staff memo to Combined Chiefs of Staff stressed the value of “The economic and moral” effects).

The last point was taken up by Dr Caddick-Adams. On 19 May 1943, Churchill addressed a joint session Congress in Washington. The dramatic results of the operation strengthened both his credibility and that of Britain as a whole. Within the American political and military establishments, there were strong proponents of defeating Japan before Germany. Churchill’s advocacy of the ‘Germany first’ option gained considerable force from Chastise’s success; the raid illustrated British determination and capability. Professor Grove agreed on the value of the resulting political capital but noted that the operation was not planned for such a reason.

*Photos By Imperial War Museum of London.