Why eight-inch guns need not pierce Bismarck's belt

At what range could an eight-inch gun penetrate Bismarck's main armor belt?

Possibly only at very close range, but cruisers would gain more by firing from about 20,000 yards and shredding Bismarck's bridge, fire-control positions, funnels, and other upperworks.

An eight-inch shell does not have to penetrate Bismarck's 12.6-inch main belt to be useful. Sustained cruiser fire from safer range could wreck command, sensor, and fire-control spaces in the extensive superstructure, degrading the battleship even while its central armor remains intact.