No. 617 Squadron (RAF): Second World War

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No.617 Squadron is undoubtedly the most famous RAF squadron of the Second World War, earning that fame on its very first operational sortie, the famous dams raid of 16/17 May 1943. The 'dambusters' went on to become a highly accurate precision bombing squadron, reserved for special targets – either small scale, difficult to hit or that required the use of Barnes Wallis's other special bombs of the Second World War, the Tallboy and Grand Slam.

The squadron was formed on 21 March 1943 as an 'elite within a elite' with selected crews. Its original purpose was to use Barnes Wallis's 'bouncing bomb' in a raid on several Ruhr dams. The hope was that the destruction of these dams and the resulting loss of water would have a devastating impact on German industrial potential.

617 Squadron Bombing Brest, 8 August 1944
617 Squadron Bombing Brest, 8 August 1944

The new squadron was led by Wing Command Guy Gibson, already a very experienced bomber pilot. The crews were amongst the best in Bomber Command. The operation required then to train in low level flight and navigation and to perfect the demanding run-ins, different for each dam. The mission was flown on the night of 16/17 May 1943 and was a costly success. Eight of the nineteen aircraft were lost, and only three of their crew survived. The Möhne and Eder Dams were breached, causing short and medium term disruption and water rationing that lasted into the following winter. Unfortunately the Sorpe Dam was of a different type and wasn't breached, and it provided just enough water to prevent a major disaster for German production. The raid also played a part in the development of the mast bomber techniques used with great success by Bomber Command later in the war.

After the dams raid Bomber Harris insisted that the squadron remained intact and would be rebuilt for use on similar tasks. This took a great deal of effort – on 2 June Air Vice Marshal Cochrane had to tell Harris that after two weeks of effort he'd only been able to find two suitable crews, while the other group commanders had found none. The problem was that any crew that had survived for two tours and gained the level of experience required was too tired to go on. Eventually enough crews were found, but the squadron then struggled to find an effective role.

The squadron's second raid came on the night of 15/16 July 1943 when it was used to attack electrical transformer stations in northern Italy. Mist hit the targets and the raid wasn't a success. In order to reach the targets the bombers then flew on to North Africa to refuel.

The next major target was the Dortmund-Ems Canal, an important link between the Ruhr and the North Sea. A first operation with new 12,000lb standard bombs was aborted due to fog (14/15 September 1943) although one of the surviving dam-busters, D.J.H. Maltby was killed when his aircraft crashed into the sea.

The squadron tried again on the following night with even more disasterous results. Eight aircraft, led by the new squadron leader G.W. Holden made a low level attack on the canal. Five aircraft were lost, including those of Holden and L.G. Knight, another of the dam busters. After this the squadron abandoned low level attacks and began to train to carry out precision raids from high altitude.

The first high altitude operation came on 11/12 November 1943 and illustrated the difficulties of hitting viaducts from altitude. The squadron used the Stabilizing Automatic Bomb Sight for the first time, dropping ten 12,000lb bombs without success. Viaducts and similar targets would prove to be very difficult to destroy until Barns Wallis's 12,000lb 'tallboy' bomb entered service.

The squadron's increasingly impressive accuracy could count against it. On the night of 16/17 December 1943 it attacked a flying bomb site near Abbeville. All of the nine 12,000lb bombs dropped landed within 100 yards of the target markers, an impressive achievement. Sadly the markers were 350 yards from the target which was thus undamaged (the same happened in another attack on a flying bomb target on 30/31 December). The requirement for accuracy also meant that a number of raids were aborted – an attack on an armaments factory near Liege on 20/21 December being one example. When low cloud obscured the target markets the squadron turned back and carried its bombs home.

By this point No.617 Squadron was beginning to look like a unit without a purpose. Low level raids were too costly, while the Oboe navigation system wasn't quite accurate enough to allow target markets to be placed on small targets. The squadron's new commanding officer, Wing Commander Leonard Cheshire, believed that the best way to solve this problem would be for the squadron to carry out its own marking using low flying aircraft to achieve accuracy. On the night of 8/9 February 1944 he was allowed to try this out officially for the first time, using a Lancaster as the marker. The target was the Gnome & Rhône aircraft engine factory at Limoges, an important target but one that was too close to French civilian houses for Bomber Command to attack by conventional methods. The Germans must have shared this opinion, for the factory was only defended by two machine guns. Cheshire took advantage of this to buzz the factory twice to give the French workers a chance to escape. He then accurately dropped his markers and eleven more Lancasters from the squadron bombed on target, knocking out production at the factory.

The squadron now began a series of accurate attacks on industrial targets in occupied Europe. An aircraft factory at Albert was attacked on 2/3 March, the La Ricamerie factory was attacked on 10/11 March, the Michelin tyre factory at Clermond-Ferrand on 16/17 March, an explosives factory at Bergerac on 18/19 March and another at Angoulême on 20/21 March, an aircraft engine factory at Lyons on 23/24 March. Most of these raids also involved aircraft from other No.5 Group squadrons.

On the night of 4/5th April 1944 Cheshire repeated the low level marking experiment this time using a Mosquito for the low-level marking of an aircraft factory at Toulouse. Cheshire's aircraft was hit repeatedly by German fire but survived intact and he was able to place his target markers accurately. The target was then attacked by 144 Lancasters from No.5 Group. This was one of a series of exploits that helped win Cheshire his Victoria Cross. After the success of these two raids 617 Squadron used the low level marking technique on a large number of occasions without losing any of its smaller aircraft (75 Mosquito sorties and six Mustang sorties without loss). No.617 Squadron adopted the low level marking technique, and eventually so did No.5 Group, although it wasn't used by No.8 Group's Pathfinders and the main bomber force. The success of this raid saw No.5 Group given the status of an independent force within Bomber Command, a sign that 'Bomber' Harris was more flexible than is often claimed.

As the D-Day invasion got closer Bomber Command spent more of its time attacked targets in France. On 10/11 April No.617 attacked a signals depot at St-Cyr.

A different type of operation was carried out in 24/25 April when the squadron was used to drop target markers over Milan. The main target for the night was actually Munich and it was hoped that the false markers might divert some German fighters from southern Germany into northern Italy.

On the night of 5/6 June 1944 the squadron took part in Operation Taxable, part of the wider deception plan associated with the D-Day landings. This operation was designed to use 'window' (metal strips dropped from aircraft to overwhelm radar displays) to simulate a convoy 14 miles wide crossing the channel and heading for the Pas de Calas. A number of small ships towing balloons coated with materials that showed up well on radar provided a basis for the operation, while No.617's aircraft had to fly a precise slow course at 3,000ft dropping specially prepared bunches of window at precise times. No.218 Squadron took part in a similar operation at Boulogne. In order to allow the Germans to detect the false convoy the nearest radar station was only jammed intermittently.

On the night of 8/9 June 1944 Barnes Wallis's 12,000lb Tallboy bomb was dropped for the first time. This aerodynamically shaped bomb span as it dropped making it very accurate, and it was designed to penetrate the ground before exploding, creating an artificial earthquake. On the night of 8/9 June No.617 Squadron provided nineteen aircraft for an attack on a railway tunnel at Saumur while No.83 Squadron was to attack a bridge outside the tunnel. The aim was to cut the main railway line from the south-west of France to Normandy, thus delaying the movements of a Panzer division. No.83 Squadron's attack on the bridge wasn't a success, but Leonard Cheshire successfully found the cutting at the entrance to the tunnel. No.617 hit the tunnel and the surrounding area, with one bomb hitting the tunnel roof, collapsing the tunnel. The railway line wasn't opened before the German retreat and the panzers were greatly delayed.

On 14 June the squadron took part in Bomber Command's first heavy bomber daylight raid since the earliest part of the war, an attack on the E-boat base at Le Havre. 617 Squadron's role was to drop Tallboy bombs onto the concrete roofed E-boat pens. One bomb scored a direct hit and penetrated the roof doing serious damage inside. The raid was a success, with only one bomber lost and Le Havre was virtually eliminated as an E-boat base.

On 19 June the squadron attacked the major flying bomb site at Watten, dropping fifteen Tallboys on the target, twelve of which landed with 100 yards of the aiming point. On the following day the squadron attempted to bomb a V-1 store in a quarry at Wizernes but bad weather meant that the bombs had to be brought home. The squadron returned to Wizernes on 24 June, this time scoring a number of direct hits. A flying bomb store at St-Leu-d'Esserent near Paris was attacked on 4 July, and a site at Mimoyecques on 6 July. After that last raid Leonard Cheshire was withdrawn from operations for a rest, having completed four tours and flown on 100 operations.

On 31 July the squadron took part in a larger attack on a V-1 storage site in a railway tunnel at Rilly-la-Montage. This time the Tallboy bombs caved in both ends of the tunnel. As a result of these and other similar raids the Germans were forced to abandon the massive V-1 bases they had constructed and use smaller more mobile launching sites.

Bomb damage to U-boat Pens at Brest
Bomb damage to U-boat Pens at Brest

Not every 617 squadron raid was a success. On 4 August the squadron tried to destroy a bridge at Étaples using 1,000lb bombs. Despite some accurate bombing the bridge survived. An attack on the U-boat pens at Brest on 5 August was more successful, with six Tallboy hits on the concrete pens, and two more hits were scored on the U-boat pens at Lorient on 6 August. The U-boat base at La Pallice was the next target, on 9 August.

The squadron was involved in the destruction of the German battleship Tirpitz. In September 1944 she was moored in Altenfjord and was out of range from the UK. In an attempt to solve this problem Nos.9 and 617 Squadrons flew to Yagodnik, near Archangel, where they received unusually enthusiastic support from their Soviet hosts. The attack (Operation Paravane) was made on 15 September but the German smoke screens prevented most of the aircraft from hitting their target. One Tallboy did hit home, causing significant damage. The Tirpitz was repaired and in a fatal error moved to Tromso to be repaired.

This brought her into range of home based bombers. Clouds foiled a first attack on 29 October, but on 12 November Nos.9 and 617 Squadrons got their chance. The smoke screen didn’t deploy in time and the Tirpitz was hit by three Tallboys. This time the damage proved fatal and the Tirpitz capsized.

On the night of 23/24 September the squadron returned to the Dortmund-Ems Canal, the site of its second costly raid back in 1943. This time the squadron used Tallboys and scored two direct hits which drained six miles of the canal. The canal, which linked the Ruhr to the Ems River and thus the North Sea, was cut until November. When it was repaired bomber command returned and breached it again.

The Tallboy bombs were always in short supply, as seen on 3 October when the squadron was allocated to the force attempted to breaching the dykes around Walcheren Island. When 617 Squadron arrived over the target enough damage had been done and so Wing Command Tait decided to bring the precious bombs back home.

On 7 October the squadron returned to a dam, this time the Kembs Dam on the Rhine.  This time the aim of the operation was to prevent the Germans releasing a large amount of water as the American and French armies reached Mulhouse. The raid involved two forces – a high group to draw flak and a low group that was to drop their Tallboys accurately onto the lock gates. The raid was a success although two aircraft were lost.

On 15 December the squadron bombed the E-boat pens at Siegen. On 29 December the target was the E-boat pens at Rotterdam.

1945 began with an attack on the U-boat pens at Bergen (with No.9 Squadron) on 12 January. Three Tallboys penetrated the 3.5 meter thick concrete roof of the pens, an impressive vindication of Barnes Wallis's design. Two U-boats were damaged (U-775 and U-864) but the squadron lost three aircraft. On 3 February the target was the U-boat pens at Poortershaven in Holland, believed to be in use by midget submarines. The pens at Ijmuiden were visited on 8 February.

Bielefeld Railway Viaduct, 1945
Bielefeld Railway Viaduct,
In the last months of the war Barnes Wallis's 22,000lb 'Grand Slam' bomb finally entered service. It was used for the first time on 14 March against the Bielefeld viaduct, destroying that target. Just as Barnes Wallis had hoped his giant bomb had caused an artificial earthquake which had destroyed the viaduct. No.617 also destroyed the Arnsberg viaduct in two raids on – an unsuccessful attack on 15th March and a successful Grand Slam attack on 19th March. The Arbergen Railway Bridge was cut on 21 March and the bridge at Nienburg on 22 March.

The Grand Slam bomb was also effective against thick concrete protection. On 27 March the squadron attacked a U-boat shelter on the River Weser north of Bremen. The shelter had a 23ft thick concrete roof, but two Grand Slams penetrated the concrete and wrecked the nearly completed shelter, which was thus never used.

7 April saw the squadron make a rare attack on German shipping, destroyed some ships that had slipped past the naval blockade on the Dutch coast and reached Ijmuiden. On 9 April U-boat pens were the target, this time at Hamburg, where a mix of Tallboys and Grand Slams were used. German warships were the target on 13 April when Nos.9 and 617 Squadrons attempted to attack the Prinz Eugen and Lützow at Swinemünde, but this time bad weather caused the raid to be cancelled. The German warships were protected by the weather for a second time on 15 April. Prinz Eugen survived the war, but on 16 April the squadron finally reached Swinemünde. One tallboy scored a near miss on the Lützow, but this was enough to tear a hole in her hull and she sank in shallow water.

On 19 April Nos.9 and 617 Squadrons attacked coastal batteries on Heligoland, again hitting their targets.

The last Tallboy raid of the war came on 25 April when 617 Squadron provided sixteen Lancasters in a force of 359 that attacked Berchtesgaden. This may seem like overkill now, but at the time there was real concern about the possibility that the Germans might retreat into an 'alpine redoubt' and try to make a brutal last stand.

During its two years of existence No.617 Squadron took part in 100 bombing raids, flying 1,478 Lancaster sorties. A total of 32 aircraft were lost during these raids, not dis-similar to the loss rates in normal squadrons. However thirteen of 617 Squadron's loses were concentrated in two raids (the dams and the Dortmund-Ems Canal raids). In the remaining ninety eight raids their loss rate was only 1.3%, at the lower end for a Lancaster squadron.

After the end of the war in Europe No.617 Squadron was allocated to 'Tiger Force', the RAF contribution to the war against Japan. Although Tiger Force was disbanded after the Japanese surrender No.617 Squadron did reach India, although not until January 1946. It returned to the UK in May and survived until 1955. A second incarnation lasted from 1958 until 1982 and a third was formed in 1983.

March 1943-June 1945: Avro Lancaster I and III
June 1945-September 1946: Avro Lancaster VII

March-August 1943: Scampton
August 1943-January 1944: Coningsby
January 1944-June 1945: Woodhall Spa
June 1945-January 1946: Waddington

Squadron Codes: AJ (1943-1945), KC (1945-1952)

March 1943-: Special purpose bomber squadron, Bomber Command

Part of
21 March 1943-: No.5 Group; Bomber Command


Bomber Offensive, Sir Arthur Harris. The autobiography of Bomber Harris, giving his view of the strategic bombing campaign in its immediate aftermath. Invaluable for the insights it provides into Harris’s approach to the war, what he was trying to achieve and the problems he faced. Harris perhaps overstates his case, not entirely surprisingly given how soon after the end of the war this book was written (Read Full Review)
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How to cite this article: Rickard, J (13 April 2012), No. 617 Squadron (RAF): Second World War,

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