The United States Navy's s were designed specifically to counter the "Mogami" class, and as a result had a very similar armament to the pre-refit "Mogami"s, in a nearly identical layout, though the US-pattern Mark 16/1 triple 6 in /47 Turret weapon was semi-automatic, with a higher rate of fire and the three weapons in each turret mounted in a single sleeve. Japan's choice of the 155 mm gun caliber is curious, as Japan already had a 6-inch (152 mm) weapon in service, of nearly equal performance. In spite of the resulting multiplicity of similar gun calibers, Japan resented the 5-5-3 treaty ratios, and had vowed to build to the very limit allowed by the 1922 Washington and 1930 London Naval Treaties. As the French had already used a 155 mm main battery in the three s (1922–1926), this became the largest gun caliber allowed for light cruisers under the 1930 London Naval Treaty.