The ships' armor protection was improved over earlier designs. The belt and barbette armor was increased by an inch compared to an earlier version of the twelve-gun battleship. A new protection scheme for the funnels was devised, after the Russian experience at the Battle of Tsushima three years before had highlighted the risk of a destroyed exhaust system. The designers also emphasized the need for improved underwater protection. As a result, the "Wyoming"s design incorporated a torpedo bulkhead, the first time the feature was included on an American battleship design. Congress approved two new battleships, BB-32 and BB-33, on 3 March 1909. Design 502 later proved to be the basis for the subsequent class of battleships, the s.