 When the Fusō class was completed , the ships ' armor was " typical for a pre @-@ Jutland battleship " . As built , the armor accounted for a displacement of 8 @,@ 588 long tons ( 8 @,@ 726 t ) , approximately 29 % of the class 's total displacement . Their waterline armor belt was 305 to 229 millimetres ( 12 to 9 in ) thick ; below it was a strake of 102 mm ( 4 in ) armor . The deck armor ranged in thickness from 32 to 51 mm ( 1 @.@ 3 to 2 @.@ 0 in ) . The turrets were protected with an armor thickness of 279 @.@ 4 mm ( 11 @.@ 0 in ) on the face , 228 @.@ 6 mm ( 9 @.@ 0 in ) on the sides , and 114 @.@ 5 mm ( 4 @.@ 51 in ) on the roof . The barbettes of the turrets were protected by armor 305 mm thick , while the casemates of the 152 mm guns were protected by 152 mm armor plates . The sides of the conning tower were 351 millimetres ( 13 @.@ 8 in ) thick . Additionally , the vessels contained 737 watertight compartments ( 574 underneath the armor deck , 163 above ) to preserve buoyancy in the event of battle damage . 
