 The sixth , ninth and thirteenth salvos were straddles and two decisive hits were made on Bismarck . One shell holed her bow and caused Bismarck to lose 1 @,@ 000 tons of fuel oil , mostly to salt @-@ water contamination . The other fell short , and entered Bismarck below her side armour belt , the shell exploded and flooded the auxiliary boiler machinery room and forced the shutdown of two boilers due to a slow leak in the boiler room immediately aft . The loss of fuel and boiler power were decisive factors in the Bismarck 's decision to return to port . In Prince of Wales , " A1 " gun ceased fire after the first salvo due to a defect . Sporadic breakdowns occurred until the decision to turn away was made , and during the turn " Y " turret jammed . 
