 During their reconstruction , the armor of the battleships was substantially upgraded . Their deck armor was increased to a maximum thickness of 114 mm ( 4 @.@ 5 in ) , and a longitudinal bulkhead of 76 mm ( 3 @.@ 0 in ) of high @-@ tensile steel was added to improve the underwater protection . This brought the total armor tonnage up to 12 @,@ 199 long tons ( 12 @,@ 395 t ) , approximately 31 % of the total displacement of the Fusō class . Even after these improvements , the armor was still incapable of withstanding 14 @-@ inch shells . 
