In WWII, allied bombers tried to destroy German ultra-hardened targets, such as dams and u-boat pens.
But even 1000 pounders couldn't destroy those massive, steel-reinforced mountains of concrete.
For dams, Barnes Wallis thought up the dambuster bomb, and in May, 1943 617 Sqn. flew its Lancasters, equipped with dambuster bombs, in Operation Chastise. They took out the Möhne and Edersee Dams. To this day, the squadron is known as the "Dambusters", with motto "Apres Moi, le Deluge" ("After me, the flood").
For u-boat pens, viaducts, bridges, and other huge structures, Wallis had another idea -- a giant bomb that would penetrate the ground, explode, and create a giant crater and earthquake to disrupt the structure.
It was the Tallboy.
12,000 lbs. 21 feet long. Hardened steel casing. Designed to be dropped by Lancasters from high altitude, get to a terminal velocity near the speed of sound, and penetrate through reinforced concrete or rock or soil. It could create a crater 100 ft deep and 80 ft wide.
Lancasters were modified to carry it, and to have a special bomb sight for superior accuracy of placement.
And, again, 617 Sqn. was chosen to use the new weapon.
It proved devastating against hardened structures.
It was even used to sink the last great German warship Tirpitz, which at anchor withstood so many other attacks. Finally Tallboys through its deck and around its sides put her down.
