The Zara class was a group of four heavy cruisers built for the Italian Regia Marina (Royal Navy) in the late 1920s and the early 1930s. The class comprised the vessels Zara, Fiume, Gorizia, and Pola, the last of which was completed to a slightly different design. The ships were a substantial improvement over the preceding Trento-class cruisers, incorporating significantly heavier armor protection at the cost of the very high speed of the Trentos. They carried the same main battery of eight 203 mm (8.0 in) guns and had a maximum speed of 32 knots (59 km/h; 37 mph). Among the best-protected heavy cruisers built by any navy in the 1930s, the heavy armor was acquired only by violating the terms of the Washington Naval Treaty, which limited cruiser displacement to 10,000 long tons (10,160 t).