Italian cruiser Bolzano

Bolzano was 187.6 meters (615 ft 6 in) long between perpendiculars and 196.9 m (646 ft) long overall. She had a beam of 20.6 m (67 ft 7 in) and a draft of 6.8 m (22 ft 4 in). She displaced 10,890 long tons (11,060 t) normally and up to 13,665 long tons (13,884 t) at full load, though her displacement was nominally within the 10,000-long-ton (10,160 t) restriction set in place by the Washington Naval Treaty. She had a crew of 725 officers and enlisted men as originally configured,[1] though her wartime complement increased to 28 officers and 788 enlisted men.[2] The ship was fitted with two tripod masts, one atop the forward superstructure and the other just forward of the rear funnel. A large, rotating aircraft catapult was located amidships, between the two funnels.[1] She could carry two or three IMAM Ro.43 seaplanes for aerial reconnaissance.[2]

Her power plant consisted of four Parsons geared steam turbines, which drove four screw propellers, and were powered by ten oil-fired water-tube boilers, which were trunked into two widely spaced funnels. Her engines were rated at 150,000 shaft horsepower (110,000 kW) and produced a top speed of 36 knots (67 km/h; 41 mph). While on speed trials with a light displacement of 10,847 long tons (11,021 t), she reached 36.81 knots (68.17 km/h; 42.36 mph) from 173,772 shp (129,582 kW). Electricity was provided by generators with a total output of 1,080 kilowatts (1,450 hp).[1]

Bolzano was armed with a main battery of eight 203 mm Mod 29 53-caliber guns in four gun turrets. The turrets were arranged in superfiring pairs forward and aft. Anti-aircraft defense was provided by a battery of sixteen 100 mm (4 in) 47-cal. guns in twin mounts, four Vickers-Terni 40 mm (1.6 in) 39-cal. guns in single mounts and eight 13.2 mm (0.52 in) guns in twin mounts. Bolzano's secondary battery was revised several times during her career. Two of the 100 mm guns were removed in the late 1930s and eight 37 mm (1.5 in) 54-cal. guns were installed in their place. The eight 13.2 mm (0.52 in) guns were replaced with four 20 mm (0.79 in) 65-cal. anti-aircraft guns in 1942. She also carried a battery of eight 533 mm (21.0 in) torpedo tubes mounted in four above-water, twin launchers.[1]

She was protected with an armored belt that was 70 mm (2.8 in) thick amidships, and capped with transverse, armored bulkheads on either end of the citadel. The forward bulkhead was 60 mm (2.4 in) and the aft was 50 mm (2 in). Her armor deck was 50 mm thick in the central portion of the ship and reduced to 20 mm (0.79 in) at either end. The gun turrets had 100 mm (3.9 in) thick plating on the faces and the barbettes they sat in were 60–70 mm thick. The main conning tower had 100 mm thick sides and a 40 mm (1.6 in) thick roof.[1]

Bolzano under air torpedo attack at Cape Matapan

Upon Italy's entrance into the Second World War on 10 June 1940, Bolzano was assigned to the 2nd Division in the 2nd Squadron, along with the two Trento-class cruisers.[4] On 9 July, the ship took part in the Battle of Calabria; there, she led the line of Italian heavy cruisers as they engaged their British counterparts. She was hit by a salvo of three 6-inch (152 mm) shells at 16:05 that killed two crewmen and jammed her rudder to port, forcing her to turn in a tight circle. The shells also hit her forward superfiring gun turret, though it was still able to fire.[3][5] The hits had come from the light cruiser HMS Neptune.[6] After the two fleets disengaged, Italian aircraft misidentified the ship as a British vessel and attacked her, though they failed to score any hits. She reached La Spezia on 12 July, where her battle damage was repaired. By the night of 11–12 November, Bolzano had been moved to Taranto; she was present during the raid on Taranto that night, but was not attacked by the British torpedo bombers.[3] A wave of horizontal bombers was tasked with attacking Bolzano and the two Trentos, but their captains decided to hold their fire; as a result, the British aircraft were unable to locate the three cruisers in the darkness and they attacked other vessels.[7]

On 26 November, Bolzano and the rest of the fleet sortied to intercept a British convoy to Malta.[8] In the ensuing Battle of Cape Spartivento, Bolzano engaged the battlecruiser HMS Renown, but neither ship scored any hits before both sides broke off the action. She took part in the sweep into the eastern Mediterranean in late March 1941 that resulted in the Battle of Cape Matapan. During the battle, British torpedo bombers attacked Bolzano but she successfully evaded their torpedoes. Bolzano thereafter took part in escort duties for convoys to Tripoli for the next several months to support the Axis forces fighting the North African Campaign. The first such convoy took place on 24–30 April. Another followed a month later on 24–27 May, and two were conducted in June, on 8–9 and 25 June – 1 July. She protected a fifth convoy that steamed to Tripoli and back on 16–20 July. Convoy operations were interrupted in late August by an unsuccessful sweep to locate British warships. While returning to port via the Strait of Messina, Bolzano was torpedoed by the British submarine HMS Triumph. She was towed to Messina by a pair of tugs, where repairs were effected, lasting three months. She was back in service in time to escort another convoy to Tripoli on 8–9 November.[3]

Trento (center) and Bolzano (background) underway

Umberto, Prince of Piedmont, heir to the italian throne, visited the ship while she was in Messina on 17 July 1942. By August, the surviving Italian heavy cruisers, Bolzano, Trieste, and Gorizia had been reorganized as the 3rd Division. On 11 August, the three cruisers sortied to intercept a British convoy, but were eventually ordered back after the Luftwaffe denied air support. In the return trip, Bolzano was torpedoed by the submarine HMS Unbroken, causing extensive damage.[3] The torpedo explosion started a fire, prompting the crew to flood the forward magazines to prevent the fire from spreading to them and detonating the propellant charges stored there.[9] To keep her from sinking, her crew beached the ship on the island of Panarea.[3] The ship was listing 45 degrees and the crew had to abandon the ship. The fire burned through the next day, until some of the crew were able to return to extinguish it.[10] She remained there until 15 September, by which time damage control parties had shored up the damaged hull enough to allow tugs to tow her back to Naples, where she entered the drydock so the damage could be inspected. Temporary repairs were effected, and in October she was transferred further north, to La Spezia, where permanent repairs would be completed. While she was awaiting repairs, the Regia Marina considered rebuilding the ship into a hybrid cruiser-aircraft carrier.[3] This would have required removing the bridge structure and forward gun turrets, and splitting the forward funnel to vent on either side of the ship so a flight deck and hangar could be installed.[1] The proposal came to nothing, however, as the Italian war economy could not spare the necessary resources to repair Bolzano, let alone convert her. Piecemeal repairs were made as material became available through early 1943, but she remained out of action.[3] On 5 June, American B-17 bombers attacked La Spezia but did not damage Bolzano.[11]

On 3 September 1943, Italy surrendered to the Allies, and on 8–9 September, German troops occupied La Spezia. As the ship was still in an unusable condition, her crew did not scuttle Bolzano, instead leaving her partially afloat. During the German occupation, they cannibalized Bolzano and the also-damaged Gorizia for useful parts but otherwise did not make use of her. On the night of 21–22 June 1944, a team of British and Italian frogmen—Italy having re-entered the war on the side of the Allies—entered La Spezia using Chariot manned torpedoes to sink Bolzano and Gorizia to prevent the Germans from sinking them as blockships. They succeeded in sinking Bolzano but Gorizia remained afloat. Bolzano was formally stricken from the naval register on 27 February 1947, and in September 1949, salvage workers raised the ship and she was subsequently broken up for scrap.[3]