May 16, 2007

Operation Chastise

To remember the day, a story from home:

Almost everybody has heard of the "Dambusters", an elite Lancaster bomber unit in WWII. They have become a major part of WWII "folklore". What exactly did they do?

It all started with Dr. Barnes Wallis. Dr. Wallis was an employee of the Vickers Aircraft Company. In March 1941, he completed a paper "A note on the method of attacking the Axis powers". Wallis idea was a to use a gigantic bomb against the Germans so that any sructure would become vulnerable to aerial attacks, even if built underground. Wallis proved that a 10 ton bomb dropped at 40,000 feet would go 135 feet into a normal surface and would create no crater as all energy would be directed into an earthquake effect with highly destructive consequences. However, no one was particularly interested in what Wallis had written. No one had ever built a 10 tons bomb, no bomber had ever been built able to carry such a bomb, not to speak of a plane flying at 40,000 feet.

However, one part of his paper did attract the attention of the War Office. Wallis believed that Germany’s industrial heart could be destroyed –- literally drowned -– if the dams of the tributaries to the river Ruhr were destroyed, emptying the reservoirs and unleashing a deluge into the densely populated industrial Ruhr area. An ‘Air Attack on Dams Committee’ was formed in 1941, who decided that the primary target should be the Möhne Dam in the idyllic South Westphalian uplands of the Sauerland. The Möhne reservoir was (and still is) the main water supply for the Ruhr area. The dam was 130 feet high and 112 feet wide at its base and still 25 feet wide at the top. In July 1941, the Air Attack on Dams Committee concluded that "There seems to be no doubt that an attack on the Möhne Dam is impracticable with existing weapons."

A torpedo type bomb, too, was out of the question as the Germans had already thought of that and had protected the dam with anti-torpedo nets. The final plan Wallis came up with was, according to him, "childishly simple". He stated that a "bouncing bomb" would clear the protective nets, smash into the dam wall, stay intact and then sink to a depth of 30 feet before exploding using a hydrostatic fuse.

Lancaster bombers: An artist's understanding of the events.

Wallis received permission to develop the bomb – code-named Upkeep. The bomb was 50 inches in diameter, 60 inches long and weighed 9250 lbs. Of this weight, 6,600 lbs was RDX explosive, it was designed to be mounted across the bomb bay of a Lancaster bomber.

It was clearly not an easy bomb to deliver and an elite new bomber squadron, 617, was formed in March 1943 to deliver the goods. The crew had to release the bomb while flying at exactly 220 mph and at a height of exactly 60 feet above the water. Top-precision flying was needed to get the bomb in motion. To add to it, the crew had to drop the bomb at exactly 425 yards from the dam wall. There could only be 25 yards in either side of this figure, not to forget that German guns would be targeting them and the fact that the attack had to be carried out at night.

Wing Commander Guy Gibson (center) and his airmen.

617 Squadron was lead by Wing Commander Guy Gibson and he was allowed to select the men who were to be on the attack among those who had survived about 60 bombing raids. The operation was given the code-name Chastise. 617 Squadron undertook extensive practising sessions of low flying but none of them knew the target. This they were told at the last minute.

On the night of May 16th, 1943, nineteen Lancaster bombers took off from Scampton in Lincolnshire. They had three primary targets: the Möhne, Eder and Sorpe dams and two secondary ones, the Lister and the Ennepe dams. Of the nineteen planes, five would be held in reserve during the attacks. To achieve the correct height (altimeters using air pressure were unreliable in the mountainous terrain so close to the ground) they fixed two spotlights to the nose and tail of the Lancaster and directed their beams downwards so that they crossed 60 feet under the craft. The navigator would direct the pilot up or down until the spots touched, forming a figure 8. The bomb aimer found the correct distance from the dam by looking through a simple hand-held wooden triangle with dowel markers. When the dowels lined up with the towers on the dam he would release the bomb.

The Möhne dam immediately after the attack.

Gibson led the first attack. At 00.56 hours, the Möhne Dam was breached and by 01.54 hours so was the Eder Dam. The Sorpe Dam was attacked by planes from the reserve force but, though hit, held out.

The attack had enormous propaganda value and made Gibson a hero of national importance. In the following euphoria, the unusually high losses were forgotten. Over 50 percent of the flyers never returned; 53 men died, 13 of them Canadians.

A picture of the devastation further down the river.

Quickly, the Germans repaired the damaged dams. Steel production in the Ruhr valley doubled that year. Few remember, or know, that much more than 1,000 (the casualty numbers vary grossly depending on the source) people died in the floods following the dam bombing, many of them Ukrainian women and children, trapped in a camp below the Möhne dam.

The most important impact of the raid was that 20,000 men working on the Atlantic Wall had been moved to the Ruhr to carry out repairs to the damaged and breached dams.

Guy Gibson returned to operational duties in 1944 and was killed on a bombing raid on Rheydt (a borough of Mönchengladbach) operating as the Master Bomber, when his de Havilland Mosquito crashed near Steenbergen, Netherlands, on 19 September 1944. It was assumed for many years that he had been shot down, but following the discovery of the wreckage of his plane, it was found that his aircraft had simply run out of fuel.

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