Chastise. Max Hastings
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paper which promised that if Britain built four thousand heavy bombers, the RAF could crush the Nazis within six months, without need for assistance from the other two services.
The prime minister responded in one of his most brilliant memoranda: ‘Everything is being done to create the bombing force on the largest possible scale … I deprecate, however, placing unbounded confidence in the means of attack, and still more expressing that confidence in terms of arithmetic … Even if all the towns of Germany were rendered largely uninhabitable, it does not follow that the military control would be weakened or even that war industry could not be carried on … The Air Staff would make a mistake to put their claim too high … It may well be that German morale will crack, and that our bombing will play a very important part in bringing the result about. But all things are always on the move simultaneously … One has to do the best one can, but he is an unwise man who thinks there is any certain method of winning this war, or indeed any other war between equals in strength. The only plan is to persevere.’
The prime minister would assuredly have said the same wise things to Barnes Wallis, had he been party to the correspondence about his putative wonder-weapons. On 21 May 1941 the engineer received a letter from Sir Henry Tizard, telling him that his ideas for both the Victory bomber and the deep-penetration bomb had been rejected by the Air Staff. Wallis was distraught. His fortunes had reached their lowest wartime ebb.
What followed, albeit painfully slowly in Wallis’s eyes, reflected an important contradiction about the conduct of the Second World War. As a fighting force, man for man, from beginning to end the Wehrmacht showed itself more professionally skilful than either the British or American armies. Yet the Western Allies nonetheless contrived to make better war than did the Axis powers. An important part of the reason for this was that they empowered many of the brightest people in their societies to deploy their talents, with an imagination which the dictatorships never matched. The codebreakers of the US Navy’s Op20G and the US Army’s Arlington Hall, together with Britain’s Bletchley Park, provided conspicuous examples of this phenomenon. So, too, did a host of projects commissioned and undertaken by scientists and engineers on both sides of the Atlantic.
Although Barnes Wallis’s Big Plane, Big Bomb proposals had been formally rejected in May 1941, he nonetheless persuaded the MAP’s David Pye that he should retain access to government facilities, to continue his experiments on the ballistics of dam-breaking. Through that autumn tests continued, to determine the necessary weight of explosives, and the conditions in which they must be detonated, to contrive breaches in huge structures.
It was an elaborately formal age. Many of the papers in what became a mountainous correspondence between Whitehall’s civilian and service departments about the engineer’s infernal machines began as did this one to an under-secretary of state: ‘Sir, I have the honour to state that consideration has again been given recently to the possibility of breaching one or more of the important canals in North West Germany.’ The engineer concerned was referred to ‘as Mr B.N. Wallis of Vickers’. The writer signed himself ‘your obedient servant’.
From the £2,000 budget then allocated to Wallis’s activities by the MAP, money was found to buy from Birmingham City Council a small dam at Nant-y-Gro in Powys, North Wales, rendered redundant by the construction of a larger replacement. A key figure in the experiments that followed was Arthur Collins, a scientific officer in Harmondsworth’s ‘Concrete Section’, who made a breakthrough. For years it had been assumed, not least by Barnes Wallis, that an enormous explosive charge would be necessary to destroy a dam such as the Möhne. Yet experiments convinced Collins, who in turn persuaded Wallis, that a relatively small charge might achieve a wholly disproportionate result if it was detonated sub-aqueously and close to the target, using a timer or a hydrostatic pistol: it could thus harness the power of the water mass to channel the force of the blast. Here was the phenomenon identified as a threat back in 1939 by the German official responsible for his country’s north-western dams. Both Collins and Wallis became increasingly fascinated by the physics of explosions, and especially by the scope for harnessing the power of water, and indeed of earth, dramatically to increase the impact of underwater or underground explosions – the ‘conservation of suspended energy’ that would eventually make possible Operation Chastise.
In the course of 1941 and 1942, Wallis pursued enquiries about Germany’s dams through patent agents in Chancery Lane, and about hydro-electric control mechanisms via an engineering firm in Kilmarnock. In April 1942 – Holy Week, as it happened – experiments assisted by his children, using marbles projected into an old galvanised washtub on the terrace outside his home at Effingham, shifted his attention from deep-penetration ‘earthquake’ charges towards the notion of much smaller spherical bombs, bowled – in cricketing parlance – or ricocheted – to use Wallis’s original choice of word – towards German dam walls. Here, he was thinking in a fashion not dissimilar from Finch-Noyes and Pemberton-Billing. He envisaged two related, but different weapons: a larger model for attacking dams, later codenamed ‘Upkeep’, as it will hereafter for convenience be called; and a smaller version, to be codenamed ‘Highball’, for use against shipping.
Sir Charles Craven, a former Royal Navy submarine officer who was now chairman of Vickers, did not explicitly bar Wallis’s spare-time work on futuristic weapons. He emphasised, however, that it must not interfere with the engineer’s day job, developing the Windsor bomber. In post-war evidence to the Royal Commission on Awards to Inventors, Wallis stated that ‘the inception of the [bouncing bomb] was the result of private experiment and work outside the scope of his normal employment and that this work was carried out against the wishes of his employers’. He subsequently expanded on this theme, saying that ‘had he not persisted in his efforts to interest the authorities in the face of continued discouragement and even contrary to the wishes of his own Directors, the attack on the dams would never have been made’. In the narrative that follows, it should not be forgotten that, until the last stage of the development of Wallis’s revolutionary weapons, his work on them represented, in the stern view of his employers, a spare-time indulgence.
3 FIRST BOUNCES
In the late spring of 1942, Barnes Wallis reported to the MAP and the Air Ministry that he believed he could overcome a critical problem – accurately to deliver a charge from a fast-moving bomber against a target protected with anti-torpedo nets – by bouncing a bomb across the water in the fashion he had explored with marbles on his terrace at Effingham. Moreover, a century and a half earlier Vice-Admiral Horatio Nelson and his fellow Royal Navy commanders had shown the way, exploiting the technique of bouncing cannonballs across the sea to pummel French warships. At the end of May, Wallis set off with his secretary, former British ladies’ rowing champion Amy Gentry, for Silvermere Lake near Cobham to test the potential of using a catapult, much more sophisticated than a child’s toy, to bounce small projectiles down a test tank. In the course of these experiments they found that, if a golf-ball-sized object was backspun on release, it would ‘ricochet’ far more vigorously. Vickers’ experimental manager George Edwards, a keen cricketer, later claimed credit for this idea, but the evidence suggests that Wallis developed it himself, and merely had later conversations about it with Edwards.
The eventual form of Upkeep was that of a large, cylindrical naval depth-charge. Until late April 1943, however, Wallis envisaged its shape as almost or absolutely spherical, the huge canister containing the charge being encased in an outer shell of wood. It was also at times described as a mine, which became part of its cover story in official correspondence and later news coverage. Since legend, however, knows the dam-busting weapon as a bomb, that is how it will continue to be described in this narrative.
Wallis told Fred Winterbotham that he saw every reason to believe that the new weapon’s destructive principles would prove as applicable to enemy shipping as to dams, locks and suchlike. Thus, on 22 April 1942 Winterbotham accompanied the engineer to discuss the project with Professor Pat Blackett, the exceptionally enlightened physicist who was scientific adviser to the Admiralty. Blackett, in turn, lobbied Tizard, who despite his opposition to Wallis’s big-bomb project a year earlier was now sufficiently excited to visit him at Burhill on the 23rd. Tizard thereafter supported Wallis’s request for access to