The Story Behind The Card Series 2 No. 6 Operation Chastise

Outlines of this WW2 operation, often part fictional have been plentiful in Postwar literature, TV and Film. I shall attempt to avoid such well known scenarios and dig a little deeper into the story.

Surprisingly the British Air Staff first considered the Ruhr Dams as possible future targets in October 1937. Barnes Wallis stressed the importance of the Dams early in 1941 and a year later began experiments pertaining to a bouncing weapon, at first playing with marbles in a tin bath. The concept of a cylindrical bomb (it was called a mine) spinning backwards before being dropped at a low level by an aircraft was enhanced by the possible use of a new explosive named Torpex that had been the brainchild of a young scientist named S.J Pooley. Torpex was available in 1941 and it had 30% more explosive power than Amatol.

The bouncing bomb concept had been pioneered as long ago as the days of the ‘wooden wall’ battleships when British gunners pointed their cannon slightly downwards. The cannon balls would then ricochet across the sea and have a greater range.

There were many tests using elderly Wellington bombers between mid 1942 and March 1943 when a new unit was formed at Scampton. It became number 617 Squadron. Before then the Wellingtons had dropped prototype ‘bouncing bombs’ (code worded ‘Upkeep’) on the Chesil Beach lagoon in Dorset. Trials using Lancasters which had their bomb bay doors removed and had powerful Vickers Jassey hydraulic motors fitted to provide the 500 rpm backspin for the ‘Upkeeps’ were fitted. These trials included lengthy operations at Reculver and North Foreland in East Kent, Loch Striven, and a Derbyshire Reservoir. Each Upkeep mine had a total weight of 9,250 lb of which 6,600 lb was Torpex explosive.

Before the operation against the dams was finally planned the radio communications arrangements had to be decided. Bombers then did not have VHF radio and the standard TR1154 and 1155 W/T sets normally installed only worked on HF. The use of TR1196 sets which operated on VHF in fighter aircraft had to be abandoned for operation ‘Chastise’, as after nightfall the frequencies used would be severely interfered with by enemy communications on their frequencies. Instead, type TR 1143s were fitted which were on a different set of frequencies. These sets used telephony, and certain code words were chosen. Some of these were: –
Pranger = Attack Mohne , Nigger = Attack Eder, Mason = All aircraft return to base , Codfish = Jamming on button A change to Button B On HF W/T silence on the 1154 transmitters was to be maintained as long as possible but constant listening was to be on 4090 Khz. When the operation was completed a short W/T signal was to be transmitted on 3680 KHz. Nineteen aircraft took part in Chastise’ (one, number 20 was a reserve) and 8 aircraft were lost, each having a crew of 7.

The damage inflicted by the ‘Upkeep’ mines (not officially classified as bombs) included 11 factories destroyed with 114 damaged, Pumping and Power Stations put out of action, and a death toll of 1,294 of which 476 were German. The remainder were foreign workers mostly Ukrainians. Additionally 25 bridges were swept away together with the flooding of large tracts of agricultural land.

A good read is the book “Barnes Wallis’ Bombs” by Stephen Flower which has comprehensive descriptions of Operation Chastise,’ Tallboy and Grand Slam weapons.

By John Heys G3BDQ – Vital Spark December 2012.

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