Operation Chastise - The Mission

Courtesy of the RAF History Department at the Ministry of Defence

The Air Ministry originally considered the Ruhr dams as a possible target early as 1937. A number of proposals and studies were undertaken between 1938 and 1941, though none produced a proper plan with all the necessary components of a viable weapon and feasible means of delivery.

A new squadron was formed at Scampton on 21st March 1943, initially known as “X” Squadron and latterly as 617 Squadron, and the 24 year old Wing Commander Guy Gibson was personally selected to lead it by none other than Air Chief Marshal Sir Arthur “Bomber” Harris, the Commander-in-Chief of Bomber Command. Gibson had flown 71 bomber sorties and an entire tour of 99 sorties on night fighters and was already the holder of four gallantry awards - the Distinguished Service Order and bar and the Distinguished Flying Cross and bar.
Despite the “elite” tag and the presence of some very experienced airmen – e.g. the two flight commanders, Sqn Ldrs Dinghy’ Young and ‘Henry Maudslay, and experienced pilots such as Dave Shannon, ‘Hoppy’ Hopgood, Les Knight and Joe McCarthy - NOT all 617 Sqn air crew were veterans. Some had flown fewer than 10 missions and one less than 5 and some of the flight engineers on the raid were flying their first operational sortie. Not all had volunteered for 617, and not all were known to or selected by Gibson: one entire flight of 57 Squadron was simply posted en masse to 617 Squadron.

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Modified Avro Lancaster B Mk III Special known as “Type 464 Provisioning”. The mid-upper gun turret along with the bomb-bay doors was removed and callipers along with a drive motor and belt fitted in the aircraft to hold and spin the bomb. Twin spotlights were fitted [see below] along with VHF radio telephone which allowed direct speech communication between aircraft, which was not normal for bomber aircraft at the time. This would allow Wg Cdr Gibson personally to direct the raid. The final approval to start modifying just three Lancasters to conduct experiments came only on 26th February 1943 with conversion sets to be prepared for thirty, later reduced to twenty, aircraft. The first plans for the necessary modifications being drawn up on 1st March and the order for the conversion of the first aircraft being signed on 8th March.

The crews, who had trained to operate their bombers at heights above 15000’, with a measured approach to the target allowing accurate navigation, were put through an intensive training programme involving extensive low-level flying and cross-country navigation eventually moving on to do the same thing at night, flying at 150’ over water, along with bombing practice. However, night-flying at that height with no moon was a a major problem and there were not enough moonlit nights, so four aircraft were fitted with an American system involving sheets of blue celluloid inside the Perspex and orange goggles, which gave the impression of moonlight when flying in the day. The aircraft flew very low, returning with dents and bits of foliage hanging off them and on at least two occasions birds smashed through the cockpit windscreens which could have been disastrous. However, despite many close shaves there were no serious accidents.

This varied depending on the type of dam. For the Mohne and Eder aircraft approached at SIXTY feet above the water IN THE DARK flying at 220 mph. For the earthen Sorpe dam aircraft flew along the dam very low at 180 mph and dropped the bomb, without spin, in the water alongside the middle of the dam. The barometric altimeters were not sensitive enough to give that accurate a reading and in any case the pilot could not look at the instrument panel at that height for fear of hitting the water. The aircraft therefore carried two spotlights which were angled so that when the beams met on the surface of the water the aircraft was flying at sixty feet, roughly twice the height of a normal house. The navigator watched the beams and called out “up” or “down” to the pilot. Flying very fast and very low with no modern radar aids with lights burning on your aircraft to show the enemy where you were was extremely hazardous. The wingspan of a Lancaster is 102’ so there was a real danger of hitting the water as the aircraft made the tight turns on the approaches to the dams. At the Eder and Sorpe the topography of the surrounding countryside with steep hills and the dams in the valleys made the approach in the dark to drop the bomb accurately in a large bomber very, very difficult. At the Eder the aircraft had to drop down from over 1000 feet to the lake and fly a curving approach hopping over a spit of land which rose to 50 feet less than a mile from the target, and then line up at the correct height and speed, before pulling up steeply to avoid the 300 feet hill which rose precipitously immediately behind the dam. To get the Lancaster down to 60 feet round and over the spit and lined up properly at right angles to the dam at 220 mph, and then make a climbing turn to getaway in the dark, was very challenging flying. At the Sorpe the aircraft had to fly over a 180-foot hill and dip down steeply to the dam just a quarter of a mile beyond to fly along and drop the bomb before climbing out using full power over another 300-foot hill immediately behind the dam. To make matters even more difficult a tall church steeple was exactly in line with the correct line of approach to the dam. The approach at the Mohne was slightly less daunting but still involved lifting the aircraft over a spit of land which rose to some 180 feet, but did provide some cover from the flak, and then dropping down to the surface of the lake to line up on the dam about a mile away. After dropping the mine the aircraft crossed the dam and then the pilot had to turn the big bomber round to the left away from flak positions to the right.

The route to and from dams was also flown at very low level to avoid the defences. Their primitive radio navigation aids were usually jammed over enemy territory though some apparently worked up to the River Rhine – most navigation after crossing the Dutch coast was done by map reading and dead reckoning. This was extremely difficult at low level in moonlight, and very dangerous – two, aircraft hit power cables and crashed, and one hit the surface of the sea, lost its bomb and was very lucky to make it back to Scampton. Some aircraft flew beneath power cables on their way to the target and others flew along roads below the level of the surrounding trees. Others strayed off course by just a few miles, which it was almost impossible to avoid doing, but the route had been designed to avoid flak defences, though not all were known, and some of the unlucky ones who strayed in the wrong place were shot down.
Three waves of aircraft were sent to attack.
First Wave – 9 aircraft in 3 “vics” of 3. To attack the Mohne, Eder and Sorpe dams. Aircraft Captains: Gibson, Martin, Hopgood; Young, Shannon, Maltby; Maudslay, Knight, Astell.
Second Wave – 5 aircraft. To attack the Sorpe. Aircraft Captains: Barlow, Munro, Rice, Byers, McCarthy.
Third Wave – 5 aircraft. Airborne reserve. Aircraft Captains: Ottley, Burpee, Brown, Townsend, Anderson.

Of the nineteen aircraft which left Scampton eleven had made attacks, resulting in breaches at the Mohne and Eder and damage to the Sorpe. Two aircraft had returned early, five had been lost on the outward journey and one at the Mohne dam. The surviving aircraft, including one which could not find its target, still had to make their way home across hundreds of miles of hostile territory. On the return trip two more aircraft were to be shot down. The victims were two of the most senior and experienced members of the Squadron. Maudslay’s aircraft may or may not have been caught in the explosion of its own weapon over the Eder and suffered further damage. Two radio messages were heard from the aircraft after the attack and it is clear that it headed for home as soon as it had dropped its mine. Probably damaged it strayed too close to the oil refineries at Emmerich on its return journey and was shot down by the flak defences. Young very nearly made it home but fell victim to German flak batteries on the coast of Holland and crashed into the sea. There were no survivors from either aircraft. McCarthy’s aircraft also nearly came to grief when it strayed over the heavily defended marshalling yards of Hamm, flying through them so low that a member of the crew remarked that the Germans didn’t need flak they only needed to change the points. Other aircraft were fired on by flak batteries on the return journey and at the coast. In all eight aircraft from the raid were lost resulting in the deaths of 53 men: three more became PoWs.

The flooding from the breached dams affected a wide area inundating many factories and damaging or destroying power stations, road and rail bridges, and other facilities. The loss of power and water for the Ruhr, crucial to many manufacturing processes, was also significant. Among a large number of towns temporarily deprived of water were Hamm, Hagen, Bochum and Dortmund. The Germans had to draft in tens of thousands of workers to repair the damaged dams and other facilities, including at least 7000 workers removed from building the Atlantic Wall defences against Allied invasion with direct positive results a year later during the D-Day invasion. Both ammunition and coal production fell after the attack, just at the point that the Germans mounted their last significant offensive on the Eastern Front. The raid also had political consequences. Prime Minister Winston Churchill was visiting America at the time, and news of the attack’s success was telephoned through to him. He was able to make considerable capital from the attack and specifically referred to it in an address to the American Congress. American and British newspapers also made much of the attack with it appearing on the front page of British papers and the New York Times. The Germans also constructed elaborate defences at all the dams in the Ruhr and elsewhere, diverting considerable military and construction resources in the process. These included anti-aircraft batteries covering every dam – prior to the raid only the Mohne had any guns protecting it. The dams were also protected by mine barrages, ramps to deflect Upkeep mines, and wire net curtains strung in front to down low flying aircraft. Although the human cost of the raid was high, and unsustainable on a regular basis, it should be remembered that it represented less than a 1000th of Bomber Command’s total losses, and the results of the attack, politically, economically and militarily undoubtedly made it worthwhile.


Air crew decorated 34
Victoria Cross – 1; Distinguished Service Order – 5; Distinguished Flying Cross – 10; Bar to Distinguished Flying Cross – 4; Conspicuous Gallantry Medal – 2; Distinguished Flying Medal 11; Bar to Distinguished Flying Medal – 1.