 The design of the Borodino @-@ class ships was modified as a consequence , which slowed their construction . Deck armour was reinforced with extra plates , the turret roofs were increased to a thickness of 150 mm ( 5 @.@ 9 in ) , and the side and roof of the conning tower were increased by 100 mm ( 3 @.@ 9 in ) and 125 mm ( 4 @.@ 9 in ) respectively . To compensate for the additional weight , the rear conning tower was removed entirely and the thickness of the main belt was reduced by 4 @.@ 5 mm ( 0 @.@ 18 in ) . Mortise and tenon joints were introduced between the armour plates along their vertical edges to better distribute the shock of a shell impact and to lessen the stress on the supporting hull structure . The launching of the first pair of ships was postponed by six months because of these changes , plus delays imposed by the large number of ship orders already in hand . 
