Grand Slam Raids

Aware that their largest bombs had still little effect on the enormous concrete structures the Germans had built to protect their U-boat pens and V weapons stores. Other larger structures where also unaffected by conventional bombs. The RAF developed a massive 22,000 lb bomb known as the Grand Slam.

Railway Viaducts, 14 March 1945

Bielefeld viaduct after the earthquake effect of the Grand Slam bomb32 Lancasters and 1 Mosquito of 5 Group, with 4 Oboe Mosquitoes of 8 Group, to attack the Bielefeld and Arnsberg viaducts. 28 Lancasters dropped Tallboy bombs and the 617 Squadron Lancaster of Squadron Leader C. C. Calder dropped the first 22,000-lb bomb, named the Grand Slam, at Bielefeld. The Arnsberg viaduct, 9 Squadron's target, was later found to be undamaged but more than 100 yards of the Bielefeld viaduct collapsed through the earthquake effect of the Grand Slam and Tallboys of 617 Squadron. The Bielefeld raid was a success with no aircraft lost.

Farge, 27 March 1945

The inside of the U-boat pens at Farge, showing the penetration achieved by the 'Grand Slam' bombs through the 23 feet of concrete that formed the pen roof.115 Lancasters of 5 Group attacked an oil-storage depot (95 aircraft) and a U-boat shelter (20 aircraft of 617 Squadron) at this small port on the River Weser north of Bremen. Both attacks appeared to be successful. The results of the raid on the oil depot were not known because this target was attacked with delayed-action bombs so that clouds of smoke would not obscure the target. The U-boat shelter was a particularly interesting target. It was a huge structure with a concrete roof 23 ft thick. It was almost ready for use when 617 Squadron attacked it on this day and penetrated the roof with 2 Grand Slams, which brought down thousands of tons of concrete rubble and rendered the shelter unusable. No aircraft were lost in these attacks.

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