Grand Slam Bomb

Most bombs dropped from aircraft during the Second World War ranged from 100lb to 4,000lb in weight. Barnes Wallis carried out experiments in developed much larger bombs and eventually he produced Tallboy, a bomb that weighed 12,000lb. This bomb, also known as the earthquake bomb,was successfully used against V1 Flying Bomb launch sites and in the sinking of Germany's giant battleship, Tirpitz, on 12th November, 1944.

In 1945 Barnes Wallis developed the 22,000lb Grand Slam. This bomb was so heavy it could only be carried by a specially adapted Avro Lancaster. The first one was dropped on Germany on 14th March, 1945.

Primary Sources

(1) Arthur Harris, Bomber Command (1947)

We already had Wallis's 12,000 Ib. medium capacity bomb, which was capable of breaking through the roof of a railway tunnel or a very thick concrete roof, and when the success of this bomb was proved Wallis designed a yet more powerful weapon, the 22,000 Ib. bomb, the most destructive missile in the history of warfare until the invention of the atom bomb. This 22,000 Ib. Bomb did not reach us before the spring of 1945, when we used it with great effect against viaducts or railways leading to the Ruhr and also against several U-boat shelters.