For the 1931 Fleet Replenishment Program, believing themselves understrength in cruisers, the IJN chose to build to the maximum allowed by the Washington Naval Treaty. This resulted in the choice of guns in five triple turrets (a first for Japan) in the "Mogami"s, also capable of 55° elevation, making the "Mogami"s one of the very few classes of cruiser to have a dual purpose (DP) main battery; this was coupled with very heavy anti-aircraft protection, as well as the standard reloadable, turreted torpedo launchers, also unique to the IJN.