Chastise. Max Hastings

the RAF’s 1937–38 dream, of an assault upon Germany’s dams.

      The array of brass assembled at the MAP on the afternoon of 26 February 1943 was told that the chief of air staff had given his assent, or rather had issued an order, to proceed with immediate development of Upkeep. Portal wrote: ‘I think this is a good gamble.’ The reaction of Sir Charles Craven, who was also present, is unrecorded. He must have felt privately foolish, if not furious, following his ugly dressing-down of his designer four days earlier. What the CAS demanded, however, Vickers must seek to provide.

Linnell, too, can scarcely have enjoyed announcing – against his own strong personal conviction – the decision to prioritise Upkeep over the Windsor bomber. ‘The requirement for bombs,’ this MAP potentate now said, ‘has been stated as one hundred and fifty to cover trials and operations’ – one hundred and twenty were eventually made. It was further stated that studies of the German dams showed that 26 May – just three months ahead – was the latest date in 1943 on which they could plausibly be attacked. It would thus be necessary to build thirty ‘Provisioning’ Lancasters, as they had been codenamed, and to produce a sufficiency of bombs by 1 May, to provide reasonable time for aircrew training for the operation. The MAP’s budget for research on Upkeep, which in August 1942 had been raised from £2,000 to £10,000, was now further increased to £15,000, and later again on 1 April to a princely £20,000.

While Portal made a personal commitment that enabled Upkeep to be unleashed, it deserves emphasis that he placed a relatively modest bet. Only air-power fantasists could suppose that a single squadron of Lancasters, a maximum of twenty bouncing bombs, would cripple the entire water system of the Ruhr, an aspiration demanding a much larger force even if Wallis’s weapons were half-successful – almost no new weapons system in history has performed better than that. Yet a squadron was all that the Air Ministry would authorise, in the face of Harris’s virulent hostility, a limited supply of aircraft and uncertainty about the viability of Upkeep. British war-makers have for centuries displayed a weakness for ‘gesture strategy’ – deploying a disproportionately small force as a means of displaying interest in fulfilment of a disproportionately large objective. Mass matters, however, to the success of all military operations, and in this case it would be lacking. Though the RAF neither then nor later admitted this, its commitment to an assault on Germany’s dams was marginal, a tiny fraction of the forces that set forth upon almost nightly attempts to burn cities. To borrow a modern phrase, this would be a niche operation.

      Wallis’s commitment to Upkeep, by contrast, was total, and now confronted him with a dramatic challenge. At breakneck speed he must convert his theoretical concept into a viable bomb, while work was simultaneously rushed forward on building the modified Lancasters. Avro, the plane’s manufacturers, agreed to fit the necessary electrical release gear, along with strongpoints where the bomb doors must be removed, and hydraulic power for backspin pulleys. Vickers would meanwhile make protruding retainer arms for the Upkeeps, to be attached to the strongpoints; a rotational driving mechanism; and the bombs themselves. All the latter work would be carried out at Weybridge, with Avro dispatching a team to work on the Vickers site. Wallis promised to provide working drawings of the latest version of Upkeep within ten days. Craven expressed concern about whether a revolutionary weapon of such size could be machined within the necessary time-frame.

      Before the final decision, some minor obstacles had to be swept away. By coincidence Combined Operations, then headed by the frisky Lord Louis Mountbatten, was proposing an attack on the Möhne, which Mountbatten described as ‘one of the great strategic targets’. Special Operations Executive also suggested an assault by parachute saboteurs. Both bodies’ proposals were now quashed, fortunately for those who might have been charged with implementing them, in favour of what was designated Wallis’s ‘rolling bomb’. It would be the RAF which destroyed the dams of north-west Germany. Or nobody.