The Barnes Wallis Memorial Trust






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Chairman: Gerry Carroll, Orchard House, South Duffield, Selby, YO8 6SX Telephone: 01757 638498
Charity no. 518023


BNW: "I thought of what would be an engineer's way of stopping the war and that would be to cut off the power supply to their great armament factories in the Ruhr, which involved bombing and destroying the dams because you know it takes 150 tons of water to make 1 ton of steel and if we robbed them of all their water supply they couldn't produce steel and the war would have come to an end..."

The decision to proceed with the raid on the Ruhr dams was only taken on February 26th 1943. "We were summoned to a meeting within eight weeks of the final date for bursting the dams that year, and were told to go ahead and I came out of that room feeling physically sick. I had won my battle and I had the terrible responsibility of making good all my claims and you can't imagine what a horrible feeling that is. When somebody has actually called your bluff. You are depending upon your self confidence and past experience of successes to guarantee that you can do something entirely new, which nobody has ever done before".

The first drop of a prototype bomb from a modified Lancaster was made on April 16th 1943 off the Kent coast near Reculver. Unlike the final cylindrical operational weapon, this bomb was spherical - the shape preferred by Barnes Wallis - and comprised a steel cylinder faired by wood into a spherical shape. It was unsuccessful and the wood broke away. A second drop later the same day produced the same result, but the cylindrical main part performed as intended. It was decided after a third unsuccessful attempt on April 22nd to dispense altogether with the wooden covering. Only three weeks before the actual attack, the bomb worked satisfactorily for the first time on April 29th.

The raid on the Mohne, Eder and Sorpe Dams was carried out on the night of May 16/17th 1943. Both the Mohne and Eder masonry dams were breached. And the damage to the Sorpe earth dam with the one remaining weapon was such that the Germans drained off half the contents of the lake to ensure safety.

Of the 19 aircraft of 617 Squadron that took off that May evening in 1943 only 11 returned. But Albert Speer, Reich Minister of Armaments, said, "We were in great danger. If the English had systematically destroyed all the dams in the region, our steel industry would have collapsed".


At the end of February 1943, a unique decision was taken to form a crack new squadron comprising some of the most experienced crews within No 5 Group - Bomber Command's most seasoned Lancaster Group. Its commander was Wing Commander Guy Gibson, already a veteran of 174 sorties. The new squadron, soon to be designated No 617, would be based at Scampton in Lincolnshire. Gibson would personally select his own crews, including quite a number from his old squadron, No 106, to fly a top secret operation of a very special nature.

By the date in May chosen for Operation Chastise, Gibson and his crews had spent 2,500 hours in training flying their specially modified Lancasters cross-country navigating by moonlight at low level. They practised the entirely new technique of releasing a mine from an aircraft flying at exactly 60 feet and at 232 mph over the Derwent reservoir in Derbyshire. The back-spinning cylindrical weapon was to skip over the water, bounce over nets and other defences, strike the dam, sink and detonate at 30 feet.

The correct release distance of 400 - 450 yards from the target was judged with a simple triangular sight using the known distance between the ornamental towers of the dams as a base. Two spotlights under the bellies of the Lancasters focused intersecting spots on the water surface to indicate the correct height.

Wing Commander Gibson made the first attack on the Mohne Dam releasing his mine at 28 minutes past midnight. Half an hour later, after the fifth Lancaster had attacked, he radioed NIGGER, signalling that the dam had been breached.

Gibson led the rest of his force to the Eder Dam directing them one by one into the attack. The same meticulous procedure was followed and the same extraordinary courage displayed. The final attempt by Pilot Officer Knight deeply breached the dam. The water spewed out, looking, as Gibson later wrote, like "stirred porridge in the moonlight".

Gibson was awarded the Victoria Cross. Thirty-two other aircrew received DS0s, DFCs and DFMs.


BNW: "After the dams had been burst, Sir Wilfred Freeman, the Chief Executive at the Ministry of Aircraft Production, asked me if I remembered my mad idea of a 10-ton bomb which I had put up in 1939. I said 'Yes, indeed, Sir Wilfred, I do'. 'Well', he said, 'how soon could you let me have one?' I said 'June, July August, September, October, five months if I have all the labour available in Sheffield'".

It was all very unofficial. At the Ministry of Aircraft Production, Sir Wilfred Freeman acted on his own initiative. Vickers in their turn had no contract. Within a few months, however, the RAF had the first 'earthquake' bomb. It was called 'Tallboy', weighed 12,000lbs and was a scaled down version of the 10-tonner which was proving difficult to cast and harden.

617 Squadron, the Dambusters, once chided as the one op. squadron, were the first to use Tallboy. Just after D-day, a Panzer Battalion was being rushed by rail from Bordeaux to the Normandy beachhead. Its route lay through the Saumur tunnel, but 617 Squadron got there first. One of nineteen Tallboys fell on the hill 60 yards from the mouth of the tunnel. It was one of the most remarkable direct hits of all time. It bored straight down into the tunnel itself and exploded there. Some 10,000 tons of earth and chalk collapsed into the tunnel.

854 Tallboys were dropped by Bomber Command Lancasters on targets in Germany and occupied Europe in World War 2. Tallboys sank the Tirpitz, damaged the Baltic rocket research station at Peenemunde and destroyed innumerable V1 and V2 launching pads for missiles pounding London. And Tallboys pierced the thick concrete of U-boat and E-boat pens on the French Atlantic coast.

On March 14th 1945, Squadron Leader C C Calder in Lancaster S-Sugar attacked Bielefeld Viaduct in Germany with the first of the 22,000lb Grand Slams, and completely shattered the target. Bielefeld Viaduct carried the main railway line from Hamm to Hanover and had survived 3,000 tons of bombs in previous attacks. Its destruction was a complete vindication of Barnes Wallis's theory that a near miss producing a near 'camouflet' could be more effective than a direct hit.

617 Squadron dropped all 41 Grand Slams to be released over Germany in the closing weeks of World War 2.

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