Operation Downwood was the official name for the famous attacks on German dams on May 17, 1943 in World War II using a specially developed "bouncing bomb". The Dam Busters were Royal Air Force 617 Squadron.
The mission developed out of the bomb. The bomb was designed by Barnes Wallis and developed into a working device by a team at Vickers. Wallis was an aircraft designer and had the successful Wellesley and Wellington to his credit, while working on the Warwick he also began work on bomb design with dams specifically in mind.

His initial idea was for a 10-ton bomb to be dropped from 40,000 feet, but research showed that without a direct hit a bomb would need to be uncarriably vast to breach a dam. However, a much smaller charge would suffice if it could be exploded directly against the dam wall below the surface of the water. But the major German dams were protected by heavy torpedo netting to prevent such an attack and it was Wallis's breakthrough to see a way past this. A drum-shaped bomb, spinning rapidly and dropped from a sufficiently low altitude at high speed would, for a short distance, skip over the surface of the water in a series of bounces before halting and sinking. An accurate drop could bypass the dam protection and be detonated against the dam with a hydrostatic fuse. After testing and many meetings the idea was adopted on February 26, 1943. The dams were to be bombed in May of that year, when water levels would be highest.

The operation was given to 5 Group and a new squadron was formed to undertake the mission. Initially called Squadron 'X' it was led by wing Commander Guy Gibson, a veteran of over 170 missions. A further 21 crews were chosen from 5 Group to join the new squadron based at Scampton.

The dams were to be three key dams in the Ruhr area, the Moehne and the Sorpe on the Ruhr River and the Eder Dam on the Eder River. The loss of hydroelectric power was important but the loss of water to industry, cities and canals would be of greater impact.

The WW2 aircraft were adapted Avro Lancaster Mk IIIs, dubbed Special Bs. To reduce weight much of the armour was removed as was the mid-upper turret. The substantial bomb and its unusual shape meant that the bomb doors were removed and the bomb itself hung, in part, below the body of the aircraft. It was mounted in two crutches and before dropping it was spun up to speed by an auxiliary motor.

Bombing from 60 feet at 240 mph, at a very precise distance from the target, required expert crews, intensive night and low-altitude flying training, and the solutions to two technical problems. The first was to know when the airplane was the correct distance from the target. The two key dams at Moehne and Eder had a tower at each of their ends. A special aiming device (basically a triangle similar to that created by the two towers and an airplane at the correct distance from the dam) showed when to release the bomb. The second problem was to measure the airplane's altitude (the usual barometric altimeters were insufficiently accurate). Two spotlights were mounted under the nose and under the fuselage such that their beams would intersect 60 feet from the underside of the plane. At the correct height, the two spots of light would merge into one on the surface of the water.

The bombs were delivered to the squadron on May 13, after the final tests on April 29. With promising weather reports the pilots, navigators and bomb aimers were informed of the targets on May 15, the rest of the crews on the following day.


The Attacks
The WW2 Lancasters were organised into three groups. Formation 1 was to attack the Moehne and after that aircraft still with bombs would attack the Eder. Formation 2 was to attack the Sorpe. The third group was a mobile reserve, it would take off two hours later and bomb as directed, either attacking the main dams or bombing smaller dams at Schwelm, Ennerpe and Dieml.

The operations room for the mission was at 5 Group headquarters in Grantham. The codes, transmitted in morse, for the mission were agreed on as Goner for bomb dropped, Nigger for the Moehne breached, Dinghy for the Eder breached and ?? for the Sorpe breached. The Nigger code was after Gibson's black dog that had been run-over and killed on the morning of the 17th.

The aircraft flew two routes, carefully skirting known flak hot-spots, and no more than 75 feet off the ground. Formation 1 entered continental Europe between Walcheren and Schouwen, crossed Holland, skirting the airbases at Eindhoven and Gilze-Rijen, curved round the Ruhr defences and turned north to avoid Hamm before turning to head south to the Moehne. Formation 2 flew further northwards, cutting over Vieland and crossing the Zuyder Zee before joining the first route near Wesel and then flying south beyond the Moehne to the Sorpe.

Formation 1 was of nine aircraft in three groups - Gibson, Hopgood, Martin; Young, Astell, Maltby; and Maudslay, Knight, Shannon. Formation 2 was of five aircraft, those of McCarthy, Byers, Barlow, Rice and Munro. Formation 3 consisted of the aircraft of Townsend, Brown, Ottley and Burpee. Two crews were unable to make the mission because of illness.

The first aircraft, those of Formation 2 and heading for the longer northern route, took off at 21.10, McCarthy's aircraft had a hydraulics fault and he took off in a reserve craft twenty minutes late. Formation 1 took off from 21.25.

The first casualties were soon after the craft reached the Dutch coast, Formation 2 was very badly attrited - Munro's aircraft lost his radio to flak and turned back over the Zuyder Zee, Rice flew too low and lost his bomb in the Zuyder Zee but recovered the aircraft to return to base. The aircraft of both Barlow and Byers crossed over the coast around Harderwijk and were soon shot down. Only the tardy aircraft of McCarthy survived across Holland. Formation 1 lost only Astell, somewhere over Rosendaal.

Formation 1 arrived over Moehne Lake and Gibson's aircraft (G for George) bombed first. Hopgood (M for Mother) attacked second, the aircraft was hit by flak as it made its 60 feet run and then caught in the blast of it's own bomb and destroyed. Martin (P for Peter) bombed third, his aircraft was hit but made a successful attack. Then Young (A for Apple) made a successful run and after him Maltby (J for Johnny) and then finally the dam was breached. Gibson then led Young, Shannon, Maudslay and Knight to the Eder.

The Eder valley was heavily fogged but not defended. The tricky topology of the surrounding hills made the approach difficult and the first aircraft, that of Shannon, made six runs before taking a break. Maudslay (Z for Zebra) then attempted a run, the bomb struck the top of the dam and the aircraft was caught in the blast. Shannon made another run and successfully dropped his bomb and the final bomb of the formation, on Knight's aircraft, breached the dam.

McCarthy (T for Tom) reached the Sorpe alone. It was the least likely to be breached - a vast earth dam rather than the two concrete structures successfully attacked. Despite the mist and ill-placed hills McCarthy's aircraft successfully dropped its bomb but did not breach the dam. Three of the reserve aircraft were directed to the Sorpe, Burpee (S for Sugar) never reached the dam, Brown (F for Freddy) reached the dam and in increasingly dense mist finally dropped his bomb without breaking the dam. Anderson (Y for Yorker) arrived last and the mist was too dense for him to even attempt the run. The remaining two aircraft were sent to subsidiary targets, Ottley (C for Charlie) was shot down en route while Townsend (O for Orange) successfully dropped his bomb on the Ennerpe.

On the way back only one further aircraft was lost, that of Young was hit by flak and crashed into the sea just off the cost of Holland. In all, of 133 aircrew 53 had been killed and three bailed out to be made POWs.


Bomb Damage Assessment
The Moehne and Eder lakes poured around 330 million tons of water into the western Ruhr region, mines were flooded and houses, factories, roads, railways and bridges destroyed as the flood waters spread for around 50 miles from the source. In terms of deaths only 1,294 people were killed, 749 of them Russian POWs from a camp just below the Eder Dam.

Of the surving aircrew thirty-three were decorated at Buckingham Palace on June 22, with Gibson awarded the Victoria Cross. There was five DSOs, ten DFCs and four bars, twelve DFMs and two CGMs. The squadron badge ("on a roundel, a wall in fesse, fracted by three flashes of lightening in pile and issuant from the breach, water proper") was chosen and a motto "Apr?s moi le d?luge".

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