While the “Trento” class (Trento and Trieste) was still under construction, within the high command Regia Marina dissent began to mount over the choices made during the design phase. Specifically, critics complained that the new cruisers, despite their large displacement (10,000 t, as mandate by the Treaty of Washington, also known as the Five-Power Treaty), were too lightly protected. In essence, protection had been too greatly sacrificed to the benefit of speed: a remarkable 35.6 knots during the 1929 trials. Still the actual operation speed was limited to about 31 knots.

R.N. Pola.
(Photo Molinari)

The first heavy cruiser class, the Trento, as well as the later Zara, were the result of an obsession with speed that dated back almost 70 years and that drove the Italian ships to always being a few knots faster than their foreign counterparts. It should be considered that during this period the Regia Marina did not have any operational battleship, thus these heavy cruisers, at least while the older battleships were being rebuilt and the new one built, represented the core of the fleet. Thus, the new cruiser had to be equipped with substantial armor, 200 mm, and the most powerful guns, 203 mm (8”), allowed by the treaty.

Having received a secretive consent from the head of government and the high hierarchy of the Navy to proceed with a project which would exceed the limit set forth by the aforementioned treaty, the “Comitati Progetto Navi” (the bureau in charge of naval constructions) produced a new design. Notwithstanding the original desired requirements, weight limitation (there was a limit to cheating after all) forced a reduction of the armor to 150 mm for the vertical surfaces and 70 mm for the horizontal ones. The main armament was kept at 8, 203 mm guns (8”) but the power plan was reduced from 150,000 to 95,000 HP. Still, the maximum trial speed ranged between 32.9 and 35.2 knots, while the final operational speed equaled the one of the Trento Class at about 31 knots. This high speed was mostly due to the power plan exceeding the requirements set forth by the construction specification by well over 23,000 HP. Thus, the true power for this class should be rated at about 118,000 HP. Most sources still report 95,000 HP.

Unlike the two Trento Class, and later the R.N. Bolzano, which had four shafts, the Zara Class had only two shafts. The Zara Class had eight boilers of the Thornycroft 3-drum type. Two groups of Parsons type, OTO-built, geared turbines moved two three-blade propellers.

R.N. Fiume.
(Photo Molinari)

At the end, the Regia Marina was to have a total of seven heavy cruisers that, despite their difference in design, could operate jointly. The first of the four new heavy cruisers of this class was the Fiume (build in Trieste), followed by the Zara (La Spezia), and then the Gorizia and Pola (Leghorn). The class was named after four provinces in the Italian northeast (Venezia Giulia). Fiume, Pola and Zara had been added to the territory in 1924, while Gorizia was created in 1927. After the war, all but the last one were lost to Yugoslavia (later Slovenia and Croatia) and renamed Rijeka, Pula and Zadar.

On the Zara class the armor was thick enough to withstand hits from guns equal to her own (they were designed to fight directly other heavy cruisers), resulting in the best armored cruisers in the world at the time. This was an important achievement because the standard for many of the Washington Treaty cruiser was a much lighter armor belt, and even less armor for the turrets and barbettes. Theorists assume that a 150 mm armor plate was not enough to withstand an incoming 203 mm armor piercing naval shell; this theory was never tested on these ships, but during the war, lighter British cruisers kept their distance from these frightening engineering marvels.

To achieve this improved armor, the Zaras were almost 2000 t heavier (as standard displacement) than the limit set forth by the treaty. In addition to the armored main belt, up to 150mm thick, there was also a very thick main deck armor of up to 70mm. Turrets and barbettes were also protected by 100mm armor. In addition to this armor, there was even another series of minor armors: the upper deck was 20mm, and the flank hull above main belt was 30mm. Almost no other cruisers were equipped with two armored decks and two armored belts. This design followed, in fact, not quite a cruiser scheme, but rather the one of a small battleship. A somewhat similar design was later implemented on the Littorio class with the introduction of de-cupping plates. Of course, this was only possible by ignoring the treaty limitations under which other constructors operated with their 203mm cruisers. Only the Des Moines class ended up having heavier armor than the Zara, but these were 17,000 tons units.

R.N. Zara.
(Photo Molinari)

In 1943, the only surviving unit, the R.N. Gorizia, was hit by three bombs launched by American heavy bombers. The main deck resisted the blasts and the ship continued firing during the whole bombardment. This is the only realistic test of the effectiveness of the Zara Class armor since the other three units were lost in the Battle of Matapan in extremely unusual circumstances.

The Zaras were equipped with the new Ansaldo 203 mm 53 caliber guns, models 1927 and 1929. These guns were superior to the Trento 203/50 for rate of fire, but shared the same salvo dispersion issues. While the 203/50s were produced by Ansaldo under industrial agreements with Schneider of France, the new 203/53 were a home-grown project. The projectile’s speed, originally at 930 m/s, was later reduced to 900 m/s to address serious dispersion issues, in addition to an unusually high barrel wear (this was common to many Italian naval guns). Thus, the original range of 31.5 km was also reduced to 29 km. Each turret hosted two guns each with an independent ammunition loading system. The guns could be loaded while elevated, thus increasing the rate of fire. The secondary armament was identical to the previous class of heavy cruisers and consisted of 12 100/47 and 2 120/15. There were also some 8 37/5 and 8 13.2 machine guns. Later, some of the 100/47s were replaced with 37/54 to be used against aircrafts. In general, anti-aircraft protection remained weak.

What might have appeared as an odd design, the installation of an airplane catapult on the aft desk, was instead a well thought out compromise. Since the aircrafts on board were to provide a spotting, rather than defense service, it was not considered useful to be able to catapult planes while the forward guns were in use. Furthermore, the launching of the plane required the ship to be steered into the wind, thus making this operation almost impossible during combat. Initially the Zara received two Piaggio P6 bis reconnaissance seaplanes, later replaced by M41s, then Cant 25 ARs, then M.F.6s, and finally (1938) by Ro. 43s.

At the time of their construction, the Italian Navy did not have radar equipment, thus these ships were not equipped with any such apparatus. Possibly, the Gorizia received one of these installations of the Gufo type around 1943. Fiume and Zara were quite similar, while the Gorizia had a taller and wider forward funnel. The silhouette of the Pola was quite recognizable having the forward funnel integrated with the bridge structure.

At the beginning of the conflict, these four cruisers made up the 1st Cruiser Division which formed the more important squadron of the Regia Marina. The Zara, Gorizia, and Fiume participated in the Battle of Punta Stilo. The Pola, Fiume and Gorizia participated in the Battle of Cape Teulada. As commonly known, all but the Gorizia were lost during the Battle of Matapan. Thereafter, the Gorizia was grouped with the Trento Class units and participated in all major engagements and battles of the Mediterranean. After the already mentioned American bombardment of the Gorizia on April 10th, 1943 in the port of La Maddalena (Sardinia), the unit was sent to La Spezia for repairs and never reentered service. Sabotaged by an Anglo-Italian group of frogmen, its hull was found at the end of the conflict, semi submerged, in the harbor of La Spezia.