http://www.thirdreichruins.com/schweinfurt.htm
Schweinfurt
Schweinfurt, an industrial city of some 52,000 people located on the Main River in northern Bavaria, was a center for the manufacture of anti-friction bearings during World War II (and still is). As the U.S. 8th Air Force began to build up its strength in England in 1943, planners wished to concentrate on bombing those industrial targets that they felt would most hurt the German war effort, particularly the enemy aircraft industry. Low-friction ball and roller bearings were used in all parts of military and commercial machinery, and research indicated that roughly half of the German bearing industry was located in Schweinfurt, concentrated at four or five factory sites on the western side of town. The 8th Air Force planners felt that if they could strike hard enough at Schweinfurt, the results might cripple the German war industry.
It didn't work. And the first two attempts cost 120 B-17s.
And as fate would have it the krauts had thought ahead, staying probably twenty year's worth of bearing production in underground shelters.
All the casualties were in vain, one of the tragic stories of the greater human tragedy of WWII.