B is for… Bouncing Bombs

617 Squadron, left to right: Flight Lieutenant R D Trevor-Roper DEM; Sergeant J Pulford; Flight Sergeant G A Deering RCAF; Pilot Officer F M Spafford DFM RAAF; Flight Lieutenant R E G Hutchinson DFC; Wing Commander Guy Gibson; Pilot Officer H T Taerum RCAF

On the night of 16 – 17 May 1943, 617 Squadron of the Royal Air Force, led by Wing Commander Guy Gibson, undertook an courageous bombing raid to destroy three dams in the Ruhr valley.[1] Code named Operation CHASTISE, the dams, situated in the industrial heartland of Germany, were fiercely protected, as the Germans knew they would be potential targets. Torpedo nets in the water stopped underwater attacks, and anti-aircraft guns defended them against enemy bombers. However, the 617 Squadron had a secret weapon, the newly developed ‘bouncing bomb’.

Plans for an attack on the German dams had already been considered as early as 1937, however it took until 1942 for a weapon to be developed capable of destroying the dams. Along with this, a suitable aircraft was also needed to deliver the bomb itself. British engineer Barnes Wallis began working on plans for a bomb that could skip across water, developing the idea by experimenting with bouncing marbles and golf balls.[2] He worked out that a bomb with backspin would strike the water gently, whereas a bomb hitting the water too hard would cause it to detonate early, therefore damaging the aircraft rather than the dam.

The RAF carried out extensive tests at various sites before embarking on their mission to the German Ruhr. These revealed that the drum-shaped bomb needed to be dropped precisely from a height of 60 feet, while travelling at a speed of 232mph.[3] This momentum would allow the bomb to spin backwards across the surface of the water before reaching the dam. It would then be driven down the wall of the dam before exploding at its base.

In late March 1943, a new squadron was formed to fly the specially modified Lancaster bombers which would carry the new ‘bouncing bombs.’ Codenamed Squadron X, the aircrew was made up with airmen from Britain, Canada, Australia, New Zealand and the USA. The squadron began intensive training a month before the operation, practicing flying at low-levels and navigating during the night. 

The Mohne Dam before the war

There were thee main dams in the Ruhr area that were chosen for the attack: Mohne, Eder and Sorpe. The Mohne dam in Germany’s Ruhr valley secured the water supply for much of the surrounding area, as well as being used to generate electricity. It was thought that the destruction of this dam, along with others in the region, would therefore cause huge disruption to German war production. Both Mohne and Eder were built in such a way that any enemy aircraft would be exposed immediately on approach.

Despite this, on the night of 16 May, 133 aircrew in 19 Lancaster took off in three waves to bomb the dams.[4] Five aircraft dropped their bombs on the Mohne damn before it was breached at 12.28am. The bombs were released about half a mile from the dam, bounced five or six times, and sank just short of the wall.  The remaining aircraft attacked Eder, breaching it at 1.52am and lastly Sopre, which remained intact.  Of the 133 men involved, 53 were killed in action, and three became prisoners of war.  In Germany, approximately 1,300 people were killed as a result of the flooding.  

Although the impact on the industrial production of Germany was limited, the raid gave a significant boost to the morale of the British public. The surviving aircrew were hailed as heroes, with Gibson being awarded the Victoria Cross for his actions during the raid. Furthermore, the raid established 617 Squadron as a specialist precision bombing unit, experimenting with new bomb sights, target marking techniques and new ‘earthquake’ bombs developed by Wallis throughout the rest of the war.[5]

Avro Lancaster B Mark I (Special), PB996 ‘YZ-C’, of No. 617 Squadron RAF, flown by Flying Officer P Martin and crew, releasing a 22,000-lb MC deep-penetration bomb over the viaduct at Arnsberg, Germany

617 Squadron went on to unsuccessful attempt to bomb the Dortmund-Ems Canal in September 1943, resulting in the lost of five aircraft and the death of the Squadron’s new commanding officer.[6] After this, the squadron concentrated on high altitude precision bombings instead. Before D-Day, the squadron attacked factories, V-weapon sites and communication targets to support the allies plans to invade France. In the autumn of 1944 the squadron joined 9 Squadron in attacks with ‘Tallboy’ bombs on a German battleship. In the final months of the war, 617 Squadron made further successful strike on German rail and canal networks, costal defences and u-boat pens. Up until the end of the war, 617 Squadron maintained its position as Bomber Command’s ultimate bombing specialist.


[1] Imperial War Museum (IWM), ‘The Incredible Story of the Dambusters Raid,’ last accessed 2 April 2021, https://www.iwm.org.uk/history/the-incredible-story-of-the-dambusters-raid

[2] Hugh Hunt, ‘How a British Engineer Made a Bomb That Could Bounce On Water,’ Smithsonian Magazine, last accessed 2 April 2021, https://www.smithsonianmag.com/history/how-british-engineer-made-bomb-that-could-bounce-on-water-180969095/

[3] IWM, ‘The Incredible Story of the Dambusters Raid,’ last accessed 2 April 2021, https://www.iwm.org.uk/history/the-incredible-story-of-the-dambusters-raid

[4] IWM, ‘The Incredible Story of the Dambusters Raid,’ last accessed 2 April 2021, https://www.iwm.org.uk/history/the-incredible-story-of-the-dambusters-raid

[5] IWM, ‘The Incredible Story of the Dambusters Raid,’ last accessed 2 April 2021, https://www.iwm.org.uk/history/the-incredible-story-of-the-dambusters-raid

[6] IWM, ‘What happened to RAF 617 Squadron after the Dambusters Raid,’ last accessed 2 April 2021, https://www.iwm.org.uk/history/what-happened-to-raf-617-squadron-after-the-dambusters-raid

[Image 1] Operation CHASTIES (The Dambusters’ Raid) 16-17 May 1943, IWM, CH 18005, https://www.iwm.org.uk/history/what-happened-to-raf-617-squadron-after-the-dambusters-raid

[Image 2] Operation CHASTIES (The Dambusters’ Raid) 16-17 May 1943, IWM, CH 9679, https://www.iwm.org.uk/collections/item/object/205195107

[Image 3] Royal Air Forces Bomber Command, 1942-1945, IWM, CH 15375, https://www.iwm.org.uk/collections/item/object/205210719


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