Thursday, March 10, 2016


The Möhne dam the day following the attacks.

 Wing Commander Guy Gibson on parade during the King’s visit of May 27, 1943.

The Bouncing Bomb
Operation Chastise, the Dambuster raid against the Möhne, Eder, Sorpe and Ennepe Dams in Germany’s Ruhr industrial region, was only made possible by the ground-breaking work of the aviation designer, Dr Barnes Wallis.

Barnes Neville Wallis was born on 26 September 1887 in Ripley, Derbyshire, and was educated at the prestigious Christ’s Hospital boarding school in Horsham, West Sussex. He rose to prominence with his pioneering geodetic basket-weave method of airframe construction, which was adopted for the R100 airship in 1930 while he was working for Vickers-Armstrongs’ Airship Guarantee Company in Hull. Pierson recognised Wallis’ obvious talents and encouraged him to move into aircraft design. Wallis subsequently worked closely with Pierson on the development of the Vickers Wellesley and Vickers Wellington bombers, both of which used his geodetic design for the construction of their wings and fuselage.

It was while Wallis was working alongside Pierson that Vickers allowed him sufficient freedom to explore other ideas and he was able to work on the development of his bouncing bomb. In April 1942 Wallis wrote his now infamous paper Spherical Bomb – Surface Torpedo, in which he first put forward his idea for a bomb that could attack shipping by bouncing across the surface of water.

Initially, his idea was that the bomb should be used to attack German capital ships, including the Tirpitz, which was hidden away deep inside a Norwegian fjord. His intention was that the bomb would bounce across the water of the fjord and so avoid the torpedo nets that protected her, nets that made a conventional attack almost impossible. Not surprisingly therefore, it was the Royal Navy that first championed the proposal and encouraged Wallis to pursue it further. It was the support from the Admiralty that led to a series of trials at Chesil Beach in Dorset in January 1943, tests which eventually proved the bomb’s viability. It is widely regarded that without the Admiralty’s support the bouncing bomb may not have got off the drawing board.

It was at this time that a flurry of political wrangling took place behind the scenes of the Air Staff which threatened to put an end to the bouncing bomb. Air Vice-Marshal Francis Linnell at the Ministry of Aircraft Production was known to be sceptical about the bomb and was concerned that the time Wallis was spending on developing it would distract him from vital work needed to get the Vickers Windsor heavy-bomber into production. On 12 February 1943 Wallis learnt that Linnell was planning to request that the bouncing bomb project be cancelled. Determined to see it through Wallis wrote to a friend at the Air Ministry, Group Captain Fred Winterbottom, to see what could be done to save the bomb. His seemingly desperate letter included the phrase “help, oh help” written across the bottom.

Winterbottom wrote to Air Vice-Marshal Francis Inglis, a senior officer on the Air Staff and suggested, falsely, that the Prime Minister was interested in the bomb, that the Royal Navy were likely to move the development of the bomb forward without the Royal Air Force and implied that the Chief of the Air Staff, Air Chief Marshal Portal had not been fully briefed on the situation.
Learning of Winterbottom’s letter, Air Vice-Marshal Linnell wrote to Arthur Harris, Air Officer Commanding-in-Chief of RAF Bomber Command and warned him that a number of his precious Lancaster bombers may be requisitioned for the bouncing bomb. Furious at the potential loss of the aircraft Harris wrote a stern letter to Air Chief Marshal Portal on 18 February 1943, which suggested that he thought the weapon only existed in the imagination of those who had proposed it and that “Highball is just about the maddest proposition as any that have yet come across – and that is saying something.”

Linnell then contacted Charles Craven, the chairman of Vickers and warned him that Wallis’ actions in pressing for the bouncing bomb were putting his company’s commercial interests at risk. Wallis was put under pressure by Craven to drop the project, but, as was typical of his stubborn nature, he chose instead to resign from Vickers.

Winterbottom’s letter to Inglis, however, had remarkably managed to turn the situation around. On 19 February 1943, the day after Harris had written his letter, Inglis had ensured that Portal had been fully briefed and that he was shown the footage of the trials at Chesil Beach. As a result of this briefing Portal wrote to Harris saying: “As you know I have the greatest respect for your opinion on all technical and operational matters and I agree with you that it is quite possible that the Highball and Upkeep projects may come to nothing. Nevertheless I do not feel inclined to refuse Air Staff interest in these weapons since I think the whole conception is far simpler than that of the Johnny Walker or the Toraplane, and we know that the full size mock-up of Highball does what is claimed for it (unless the cinema lies!)” Portal then ordered an astonished Linnell to approve the bouncing bomb project.

On 26 February 1943 Linnell briefed Wallis on the proposal to attack on the dams and stated that the raid would have to take place by the full-moon in May of that year. This gave Wallis just two months to complete his development, during which time Bomber Command was required to establish and train a special squadron to undertake the mission. The new 617 Squadron was established in record time and was based at RAF Scampton in Lincolnshire, with Wing Commander Guy Gibson appointed as its commander. It has been suggested that Gibson handpicked the squadron from the ranks of former colleagues, choosing the most experienced crews. In fact Gibson had only previously known four of the pilots who joined the squadron. As for them being the most experienced, rear gunner Canadian Grant MacDonald had flown just four missions before he joined the squadron.

The Raid
On the night of 16 May 1943 nineteen Lancaster Mk III bombers from 617 Squadron, armed with Upkeep bouncing bombs, took-off from RAF Scampton to attack the Möhne, Eder, Sorpe and Ennepe Dams in Germany’s Ruhr and Eder valleys. To compensate for the size and weight of the bomb, each aircraft was specially modified, which included removing most of the internal armour and the bomb-bay doors.

The aircraft were divided into three formations. The first consisted of nine aircraft and was assigned to the Möhne Dam, with orders to then attack the Eder Dam if they had any bombs remaining. The second formation consisted of a further five aircraft and was set the task of attacking the Sorpe Dam. The third formation was made up of another five aircraft and was intended as a reserve force that took-off two hours after the first two formations had departed. The second formation was the first to take-off and left RAF Scampton at 9.28pm on 16 May. They took a longer northern route to the dams, whilst the first formation, which took off from 9.39pm in groups of three at ten minute intervals, was assigned the shorter southern route. The third formation began to take-off early the following morning at 0.09am.

Gibson led the first formation and was the first to attack the Möhne Dam. Flight Lieutenant John Hopgood made the second run, but was hit by flak as he approached the dam and was then caught by the blast of his own bomb. Gibson flew across his flight-path in an attempt to draw away the enemy’s fire, but Hopgood crashed shortly after. Two of Hopgood’s crew managed to survive. Flight Lieutenant Harold Martin then made the next run and successfully attacked the dam, followed by Squadron Leader Henry Young and Flight Lieutenant David Maltby. The dam was eventually breached and Gibson led the remainder of the first formation on to the Eder Dam, with Lancasters piloted by Squadron Leader Henry Young, Flight Lieutenant Dave Shannon, Squadron Leader Henry Maudslay and Flying Officer Les Knight.

Once over the Eder Valley the Lancasters encountered thick fog, which made lining up the next attack more difficult. Shannon made six runs at the target before he stepped aside and let Maudslay make an attempt. Maudslay dropped his bomb in the attack, but it clipped the top of the dam and the explosion damaged his aircraft. Shannon then made his next attempt, which successfully exploded behind the dam. Knight then made his next run and successfully exploded his bomb against the dam, which finally was sufficient to cause a breach.

Flight Lieutenant Joe McCarthy from the second formation, with Flight Sergeant Ken Brown and Flight Sergeant Cyril Anderson from the third formation, reached the Sorpe Dam. Unlike the other dams, which were made of concrete, the Sorpe was of earthen construction and was expected to be much harder to breach. For these attacks the Lancasters were to approach along the length of the dam, rather than at right angles, and the Upkeep bomb was not spun in the aircraft before it was dropped.

McCarthy made ten attempts at his run before he dropped his bomb. He managed a direct hit but caused very little damage. Brown made his attack, but also failed to damage the dam. Anderson abandoned his run due to the dense fog. The remaining Lancasters were then ordered on to other targets before turning for home. Pilot Officer Warner Ottley was shot down before he could reach the Lister Dam and although Flight Sergeant Bill Townsend managed to launch an attack on the Ennepe Dam his bomb did not cause any damage.

The surviving aircraft started arrive back at RAF Scampton from 3.11am. Gibson returned at 4.15am and Townsend was the last to return home, reaching the air base at 6.15am.

Of the nineteen Lancasters that left that night, eight did not make it back. The aircraft were required to fly at a perilous height of one-hundred feet for most of the journey in order to avoid enemy radar detection. As a result two of the Lancasters collided with power cables and were lost before reaching their targets, two aircraft were shot down over the Netherlands before they could reach their target and a third was shot down over Germany before it reached the dams. After the attack two Lancasters were shot down over Germany and one was shot down over the Netherlands. Fifty-three of the one-hundred and thirty-three aircrew who had left the previous evening were killed on the raid, of which thirteen were Canadian and two were Australian. There were three survivors taken prisoner-of-war, two were from Hopgood’s aircraft and the third was from Ottley’s.

A total of thirty-four air crew were recognised for their contribution to the raid and received decorations at a ceremony held at Buckingham Palace on 22 June 1943. Gibson was awarded the Victoria Cross. In addition, five airmen received Distinguished Service Orders, ten Distinguished Flying Crosses and four bars, two Conspicuous Gallantry Medals and eleven Distinguished Flying Medals and one bar.

Wallis was shocked by the loss of life amongst the aircrew of 617 Squadron, who he had got to know during the weeks prior to the raid. When the Royal Commission awarded him £10,000 for his work during the war he donated it to his old school, Christ’s Hospital, to establish the RAF Foundationers’ Trust that could pay for children of airmen killed or injured in action to study at the school.

Wallis and his wife Molly had four children and their daughter Mary married Harry Stopes-Roe, the son of the women’s rights campaigner Marie Stopes and Humphrey Verdon-Roe, co-founder of AV Roe and Company Limited, the aircraft manufacturer that designed and built the Lancaster bomber.
A special memorial to those who took part in Operation Chastise was erected at Woodhall Spa, near to RAF Scampton. In 2008 a statue of Barnes Wallis was erected near Reculver in Herne Bay, Kent, where the Upkeep bomb was tested.

A memorial was erected in Neheim, four miles from the Möhne Dam, in memory of the German dead. Figures have since suggested that in Germany the raid cost the lives of 1,294 people, of which 749 were believed to have been French, Belgian, Dutch and Ukrainian prisoners of war and labourers.

Examples of various bouncing bomb prototypes can be found at museums around the UK, including the Aeronautical Museum at Brenzett, Romney Marsh, the Brooklands Museum in Weybridge, Dover Castle in Kent, the Imperial War Museum at Duxford in Cambridgeshire and the Spitfire and Hurricane Memorial Museum at RAF Manston in Kent.

RAF 1936 Bomber Specifications

A feature of the 1936 bomber specifications that had unlooked for beneficial repercussions was the requirement that the medium bomber P. 13/36 should be capable of modification to carry torpedoes. When tenders to specification P. 13/36 were received, it was found that provision to carry two 18 in. torpedoes (which were 18 ft long) without altering the main structure of the aircraft, or losing performance, was causing design difficulties. This led the DDOR (Oxland) to review the discussion on this issue that had taken place at the two Operational Requirements Committee meetings on P.13/36. He told the DCAS (Peirse) that the Coastal Command representative had given his C-in-C’s view that the aircraft was too large and expensive for a torpedo bomber. Even so, the then DCAS (Courtney) had argued that whilst there was the possibility of a limitation on the numbers of first-line aircraft, it was desirable that every unit should be as effective in war as possible. As we have seen, a muted form of the torpedo-carrying requirement was therefore included in the requirements.

Oxland recommended that as a dedicated torpedo bomber was now under development (B.10/36 — Bristol Beaufort) the torpedo requirement should be deleted from P.13/36. Alternatively, he said, provision could be made for a limited number of the aircraft to have larger bomb doors and so on.
The Operations and Plans branches of the Air Staff did not agree with deletion of the torpedo requirement. They advised Peirse that the Admiralty had yet to be persuaded that, ‘the “B” bomb is in every way a more efficient weapon with which to attack ships’, and that a torpedo bomber version of P. 13/36 should be developed until the Admiralty was convinced otherwise. (The ‘B’ bomb was designed to be dropped in the path of a ship, sink, and then rise to strike the bottom of the ship as it passed over.)

This discussion was made redundant when the Operational Requirements branch announced that it had new information on the size of torpedoes. It now found that the Avro P. 13/36 could carry only one internally, and that in any case existing torpedoes could not be released at 150 mph from 200 ft. If this was relevant, the DCAS (Peirse) must have wondered how the idea of torpedo carrying for P.13/36 had arisen in the first place. It appears that the Operational Requirements branch had given no more thought to the operational problems of torpedo dropping than they were later found to have given to catapult launching. Peirse decided that torpedo carrying would no longer be asked of the P.13/36 bombers. Nevertheless, the long bomb bay that had been required was to prove valuable when bombs larger than the 2,000 lb were found to be needed.

A common misconception regarding RAF bomber specifications is that they always sought to combine bomber and troop transport requirements, and it is suggested that this applied to the 1936 bomber specifications. We have seen that the requirement that a heavy bomber should be designed so as to carry troops was indeed included in the first draft specification for the B.3/34 (Whitley). The Air Staff had been led to believe that this additional role could be obtained without a reduction in its performance as a bomber. It was dropped from the specification after discussions with industry, and after the DTD admitted it would result in a loss of 10 mph in speed.

The 1936 bomber specifications (B.12/36 and P.13/36) stated:
Consideration is to be given in design for fitting a light removable form of seating for the maximum number of personnel that can be accommodated within the fuselage when the aircraft is being used for reinforcing Overseas Commands.

This was certainly not demanding provision for troop carrying. Seating was to be fitted in the fuselage, not that the fuselage was to be designed to take seating. Moreover, it referred to the need to transport RAF ground crew to RAF Overseas Commands — a concomitant of the introduction of a reinforcement range into bomber requirements. Significantly, only after the 1936 bomber specifications had been issued did the Air Staff investigate using them as transports, and proposed a provisional allocation of funds for a new transport in case this was not possible. But when this proposition was discussed it was decided that one of the bombers ‘must’ be used as a transport. In a later lecture to the Higher Commanders’ Course the point was made that these bombers ‘will have all the necessary cabin space, lift capacity and range to fulfil the bomber transport primary role and its secondary functions as well’. Nevertheless, the lecturer noted that ‘by reason of the multiplicity of internal installations in the fuselage the troops may not enjoy the same degree of comfort available in present types’. Indeed, when Bomber Command officers inspected the mock-up of the Supermarine design to B.12/36, far from finding accommodation for fully armed troops, they were concerned as to whether there was adequate room for the crew. They reported that headroom throughout the fuselage was restricted, and that even the captain and navigator did not have room to stand. Clearly a troop carrying requirement did not dominate — or even influence — the design of RAF bombers.

Another aspect of the future development of the aircraft designed to the 1936 bomber specifications was of great significance. We have seen that when Sir Edward Ellington saw the Air Staff Requirement for the new heavy bomber B.12/36, he asked for 20mm cannon armament to be considered. The Air Staff advised that this was neither possible nor necessary. Their reasoning was unsound, and the policy was soon reversed, but it was then too late to modify any of the designs to the 1936 bomber specifications, although attempts were made.

When the cannon fighter (F.37/35) was devised, the replacement of eight 0.303 in. machine guns by half that number of 20mm cannon was regarded as a major increase in armament. Yet, in response to Ellington’s request for consideration of cannon armament for bombers, Oxland examined only the replacement of machine guns by the same number of 20mm cannon. From this premise he argued that for a four-gun tail turret, the extra weight of cannon so far aft of the centre of gravity was unacceptable — hardly an insurmountable obstacle for aircraft which were yet to be designed. He added that recoil loads would give grave problems except for firing almost directly astern. For a two-gun midships turret, Oxland claimed that whilst the weight would be half that of the tail turret, the weight of the ammunition needed for an aircraft which would spend long periods over hostile territory was unacceptable. We will see that this self-contradictory argument was replaced in 1938 by recognition that it was worth exchanging half the bomb load for ammunition if that made it more likely that the remainder would get through. For the nose turret, Oxland said that cannon would obstruct the bomb aimer, and would be too heavy if beam fire was wanted. He then claimed that these difficulties could be avoided because a bomber did not need the extra range of a big gun.

This argument had appeared in the Operation Requirements branch’s review of fighter and bomber armament that we noted in our discussion of fighter firepower. It reasoned that when attacked from astern the effective range of a bomber’s firing was considerably shortened as compared with that of the attacking fighter. If we think of a fighter flying directly astern of a bomber, and at the same speed, then from the moment a projectile leaves the bomber the fighter is flying towards it, thus closing the effective range. Conversely, the range of the fighter’s firing opens, because the bomber is moving away from it. This theory was irrelevant to defence against beam or frontal attacks, and therefore to midships and nose turrets. Nevertheless, Oxland claimed that it largely disposed of one of the two supposed advantages of 20mm guns. As regards the other advantage of cannon — an explosive shell — he said that the stage had not been reached ‘where this can be utilised effectively without severe disadvantages’. There had been no mention of such difficulties when he and Sorley had advocated cannon armament for RAF fighters in the previous year — they then claimed that one hit from a 20mm round could be decisive.

Little more than a year after Oxland had argued against 20mm cannon armament for the B.12/36 he was advising Plans branch of the Air Staff that bombers of the immediate future would need to be armed with 20mm guns, and later with 37—40 mm guns.96 This was confirmed in a review of bomber armament in June 1938.

Plans were made to fit 20mm cannon to Mark II versions of the Stirling, Halifax and Manchester, but by then the centre of gravity issue was decisive because it had not been designed for in 1936. Experiments with twin 20mm cannon upper and lower midships turret for the Stirling and Halifax found that it was difficult to balance the aircraft even with the tail turret omitted entirely. W.S. Farren (then DD/RDA) explained to the Air Fighting Committee in 1940 that nevertheless this was the only way of having 20mm guns on existing bombers. He said that to have cannon in a tail turret, ‘they would have to start again from the beginning’.

The outcome of the 1936 bomber specifications was remarkable. On the one hand, the prospect of catapult take-off led to a requirement for a relatively small heavy bomber to carry a very large bomb load or have a longer range than that sought in earlier specifications. On the other hand, the desire for a multi-role high-speed medium bomber with a maximum range of 3,000 miles led to a relatively large aircraft of this type. Misleading interpretations of the Air Staff’s intentions in 1936 most likely arise from a retrospective view of the development of the aircraft designed to meet these requirements. It transpired that the aircraft designed to the medium bomber specification (P.13/36) embodied the potential for development into more successful heavy bombers (Halifax and Manchester/Lancaster) than that designed to the heavy bomber specification, B.12/36 (Stirling). That this was possible can be traced to three technical features of the medium bomber specification — gross overloading with catapult take-off, fuel tankage for a range of 3,000 miles, and provision for the internal stowage of torpedoes.

Initial designs to specification P.13/36 needed to be stressed for catapulting at maximum overload, and to have internal stowage for the overload bomb and fuel load. In addition, provision had to be made for an unobstructed bomb bay if some of the aircraft were to be modified to serve as torpedo bombers. These additions to the normal requirements gave scope for the future development of the aircraft which followed from the specification after both torpedo carrying and catapult take-off had been abandoned. There was space for much larger bombs than were envisaged in 1936, and the potential for operation with large bomb loads using a longer conventional take-off run.

The first step towards the transformation of the intended medium to a heavy bomber came from Handley Page. Soon after commencing design to P. 13/36 the company concluded that the aircraft would be very similar to their on-going design to B.1/35 — the ‘Americanised’ B.3/34 heavy bomber specification. They asked the Air Ministry if they could stop work on their contract for B.1/35 and absorb it into their P.13/36 design. This was agreed.

Both the Handley Page and Avro P.13/36 bombers were initially designed to be powered by two Vulture engines as anticipated by Verney. But on Air Ministry instructions the Handley Page design was soon changed to four Merlins, and was thought to meet the P.13/36 maximum overload requirement without assisted take-off, albeit with a long conventional take-off. Avro continued with the Vulture engine, but this proved a failure, and the P.13/36 Manchester was modified to the Lancaster, also with four Merlins. Thus the Air Ministry’s misplaced faith in the catapult scheme finished back where Liptrot’s first estimates for a new heavy bomber had started — with bombers powered by four Merlins — albeit derived from requirements for a medium bomber.