Andrea Doria-class battleship

The Andrea Doria class was a pair of dreadnought battleships built for the Royal Italian Navy (Regia Marina) during the early 1910s. Completed during World War I, neither ship saw any combat during the war.

They were modernized during 1937–1940, between the wars, and both participated in World War II, at the First Battle of Sirte, and on convoy duty.

Design
The Andrea Doria-class ships were designed by Vice Admiral (Generale del Genio navale) Guiseppe Valsecchi and were ordered in response to French plans to build the s. The design of the preceding s was generally satisfactory and was adopted with some minor changes. These mostly concerned the reduction of the superstructure by shortening the forecastle deck, the consequent lowering of the amidships gun turret and the upgrading of the secondary armament to sixteen 152 mm guns in lieu of the eighteen 120 mm guns of the older ships.

General characteristics
The ships of the Andrea Doria class were 168.9 m long at the waterline, and 176 m overall. They had a beam of 28 m, and a draft of 9.4 m. They displaced 22956 LT at normal load, and 24729 LT at deep load. They were provided with a complete double bottom and their hulls were subdivided by 23 longitudinal and transverse bulkheads. The ships had two rudders, both on the centerline. They had a crew of 31 officers and 969 enlisted men.

Propulsion
The ships were fitted with three Parsons steam turbine sets, arranged in three engine rooms. The center engine room housed one set of turbines that drove the two inner propeller shafts. It was flanked by compartments on either side, each housing one turbine set which powered the outer shafts. Steam for the turbines was provided by 20 Yarrow boilers, eight of which burned oil and twelve of which burned both oil and coal. Designed to reach a maximum speed of 22 kn from 32000 shp, neither of the ships reached this goal on their sea trials, only achieving speeds of 21 to 21.3 kn. The ships could store a maximum of 1488 LT of coal and 886 LT of fuel oil that gave them a range of 4800 nmi at 10 kn.

Armament
As built, the ships' main armament comprised thirteen 46-caliber 305-millimeter guns, designed by Armstrong Whitworth and Vickers, in five gun turrets. The turrets were all on the centerline, with a twin-gun turret superfiring over a triple-gun turret in fore and aft pairs, and a third triple turret amidships, designated 'A', 'B', 'Q', 'X', and 'Y' from front to rear. The turrets had an elevation capability of −5 to +20 degrees and the ships could carry 88 rounds for each gun. Sources disagree regarding these guns' performance, but naval historian Giorgio Giorgerini claims that they fired 452 kg armor-piercing (AP) projectiles at the rate of one round per minute and that they had a muzzle velocity of 840 m/s which gave a maximum range of 24000 m.

The secondary armament on the first two ships consisted of sixteen 45-caliber 152 mm guns, also designed by Armstrong Whitworth, mounted in casemates on the sides of the hull underneath the main guns. Their positions tended to be a bit wet in heavy seas, especially the rear guns. These guns could depress to −5 degrees and had a maximum elevation of +20 degrees; they had a rate of fire of six shots per minute. They could fire a 22.1 kg high-explosive projectile with a muzzle velocity of 830 m/s to a maximum distance of 17000 yd. The ships carried a total of 3,440 rounds for them. For defense against torpedo boats, the ships carried nineteen 50-caliber 76 mm guns; they could be mounted in 39 different positions, including on the turret roofs and upper decks. These guns had the same range of elevation as the secondary guns, and their rate of fire was higher at 10 rounds per minute. They fired a 6 kg AP projectile with a muzzle velocity of 815 m/s to a maximum distance of 10000 yd. The ships were also fitted with three submerged 45 cm torpedo tubes, one on each broadside and the third in the stern.

Armor
The Andrea Doria-class ships had a complete waterline armor belt that had a maximum thickness of 250 mm, reducing to 130 mm towards the stern and 80 mm towards the bow. Above the main belt was a strake of armor 220 mm thick that extended up to the lower edge of the main deck. Above this strake was a thinner one, 130 millimeters thick, that protected the casemates. The ships had two armored decks: the main deck was 24 mm thick in two layers on the flat that increased to 40 mm on the slopes that connected it to the main belt. The second deck was 29 mm thick, also in two layers. Fore and aft transverse bulkheads connected the armored belt to the decks.

The frontal armor of the gun turrets was 280 mm in thickness with 240 mm thick sides, and an 85 mm roof and rear. Their barbettes had 230 mm armor above the deck that reduced to 180 mm between the forecastle and upper decks and 130 millimeters below the upper deck. The forward conning tower had walls 320 mm thick; those of the aft conning tower were 160 mm thick.

Modifications and reconstruction
During World War I, a pair of 50-caliber 76-millimeter guns on high-angle mounts were fitted as anti-aircraft guns. In 1925 the number of 50-caliber 76-millimeter guns was reduced to 13, all mounted on the turret tops, and six new 40-caliber 76-millimeter guns were installed abreast the aft funnel. In addition two license-built 2-pounder anti-aircraft (AA) guns were also fitted. In 1926 the rangefinders were upgraded and a fixed aircraft catapult was mounted on the port side of the forecastle for a Macchi M.18 seaplane.

The sisters began an extensive reconstruction program in 1937 that lasted until July 1940 for Duilio and October 1940 for Andrea Doria. The existing bow was dismantled and a new, longer, bow section was built which increased their overall length by 10.91 m to 186.91 m. Their beam increased to 28.03 m and their draft at deep load increased to 10.3 m. All of the changes made during their reconstruction increased their displacement to 28882 LT for Andrea Doria and 29391 LT for Duilio at deep load. The ships' crews increased to 70 officers and 1,450 enlisted men.

Two of the propeller shafts were removed and the existing turbines were replaced by two sets of Belluzzo geared steam turbine rated at 75000 shp. The boilers were replaced by eight superheated Yarrow boilers. On their sea trials the ships reached a speeds of 26.9 - 27 kn, although their maximum speed was about 26 kn in service. The ships now carried 2530 LT of fuel oil which provided them with a range of 4000 nmi at a speed of 18 kn.

The center turret and the torpedo tubes were removed and all of the existing secondary armament and AA guns were replaced by a dozen 135 mm 230 mm guns in four triple-gun turrets and ten 90 mm AA guns in single turrets. In addition the ships were fitted with fifteen 54-caliber Breda 37 mm light AA guns in six twin-gun and three single mounts and sixteen 20 mm Breda Model 35 AA guns, also in twin mounts. The 305-millimeter guns were bored out to 320 mm and their turrets were modified to use electric power, a fixed loading angle of +12 degrees, and the guns could now elevate to +27 degrees. The 320-millimeter AP shells weighed 525 kg and had a maximum range of 28600 m with a muzzle velocity of 830 m/s. In early 1942 the rearmost 20-millimeter guns mounts were replaced by twin 37-millimeter gun mounts and the 20-millimeter guns were moved to the roof of Turret 'B'. The forward superstructure was rebuilt with a new forward conning tower, protected with 260 mm thick armor. Atop the conning tower there was a fire-control director fitted with three large rangefinders.

The deck armor was increased during reconstruction to a total of 135 mm. The armor protecting the secondary turrets was 120 mm thick. The existing underwater protection was replaced by the Pugliese system that consisted of a large cylinder surrounded by fuel oil or water that was intended to absorb the blast of a torpedo warhead.

Service history
Both ships were assigned to the 2nd Division at Taranto after their completion and they saw no combat during the war. They were transferred to the 1st Division in 1918 and Andrea Doria served as the division's flagship that year.

Andrea Doria served at the First Battle of Sirte and as a convoy escort until interned after the armistice in September 1943. She served as the Italian flagship in the 1950s.

Caio Duilio was damaged at the Battle of Taranto by British aircraft. Because of fuel shortages, she was out of the war following the armistice. She was later a training ship and flagship of the Italian Navy until scrapped.