The Kirov-class (Project 26) cruisers were a class of six cruisers built in the late 1930s for the Soviet Navy. After the first two ships, armor protection was increased and subsequent ships are sometimes called the Maxim Gorky class. These were the first large ships built by the Soviets from the keel up after the Russian Civil War, and they were derived from the , being designed with assistance from the Italian Ansaldo company. Two ships each were deployed in the Black and Baltic Seas during World War II, while the last pair was still under construction in the Russian Far East and saw no combat during the war. The first four ships bombarded Axis troops and facilities after the Germans invaded the Soviet Union in June 1941. All six ships survived the war and lingered in training and other secondary roles, with three being scrapped in the early 1960s and the other three a decade later.
Design Following the October Revolution and the subsequent Russian Civil War, Soviet industry was not capable of designing large, complex warships by itself and sought foreign assistance. The Ansaldo company provided plans for the contemporary Raimondo Montecuccoli-class cruisers and a design displacing and armed with six guns in twin turrets was produced in 1933. The Italians guaranteed that the cruiser could make on trials if the size was kept under the 7200-tonne limit. The designer of the new turret managed to persuade his superiors that he could fit triple turrets to the ship while keeping it within the specified limit, and this design was approved in November 1934 as the Project 26.Yakubov and Worth, p. 83
The Soviets bought an example of, and plans for, the machinery of the later Duca d'Aosta-class cruisers and had some difficulty in adapting the smaller hull for the larger and more-powerful machinery, so much so that it delayed the start of construction. Another problem was that the Italian design had to be adapted to use the Soviet preference for a mix of longitudinal framing for the hull framing amidships and transverse framing for the ends, while also reinforcing the hull structure to withstand the more-severe weather conditions that the Soviets commonly encountered.Yakubov and Worth, pp. 83-4
The Kirovs were built in pairs, each pair incorporating some improvements over the earlier pair. These pairs were designated as the Project 26, Project 26bis, and Project 26bis2 in sequence. The differences between pairs usually related to size, armor, armament and aircraft.Yakubov and Worth, p. 85
General characteristics The Project 26 class ships were long overall. They had a beam of and at full load a draft of . They displaced at standard load, and at full load. Their single rudder meant that they were not very maneuverable. Kirov and Voroshilov were fitted with a massive tetrapod foremast, but this proved to restrict the view from the conning tower as well as the fields of fire of the 100 mm anti-aircraft guns and greatly increased their silhouette. It was reduced to a simple pole mast in the later ships and the superstructure enlarged to accommodate the fire control facilities formerly housed in the foremast.
Shortly after Kirov was launched in 1936, the two Project 26bis ships were laid down. They incorporated a number of changes from the first batch, not least of which was that they were larger. They displaced at standard load and at full load. They were only slightly longer at overall and had a deep draft of at full load. On trials they proved to be the fastest ships of the class with a speed of . Their armament was much the same as the earlier ships, although nine 61-K anti-aircraft guns were mounted rather than the six on the first pair and they were fitted to carry 150 Model 1908/39 mines in place of the Model 1912 mines.Yakubov and Worth, p. 84
The Project 26bis2 pair were still larger and displaced at standard load, and at full load. They were a tenth of a meter shorter than the Project 26 ships, although the waterline length did not change at all between any of the pairs. Their turbines proved to be slightly more powerful than those of the Project 26bis ships and propelled them at on trials. Production delays with the 100 mm B-34 dual-purpose guns forced them to use 90-K guns instead and ten 70-K anti-aircraft guns supplemented the 45 mm guns. The mines changed yet again as they could carry 100 KB or 106 Model 1926 mines.
Armament The main armament consisted of three electrically powered MK-3-180 triple turrets with three 57-calibre 180 mm B-1-P guns. The turrets were very small to fit them into the hull space available and were so cramped that their rate of fire was much lower than designed (only two rounds per minute instead of six). The guns were mounted in a single cradle to minimize space and were so close together that their dispersion was very high because the muzzle blast from adjacent guns affected each gun. The turrets weighed approximately , and the guns could be depressed to −4° and elevated to 48°. The guns fired projectiles at a muzzle velocity of ; this provided a maximum range of around , depending on ammunition and gun type. Normally, 100 rounds per gun were carried, although an additional four rounds per gun could be carried at overload by the Project 26 ships only.
The secondary armament consisted of six single 56-caliber B-34 anti-aircraft guns with 325 rounds per gun fitted on each side of the rear funnel in all ships except the Project 26bis2 which used eight single 52-caliber 90-K guns with 300 rounds per gun when the B-34 program ran into problems. Light AA guns initially consisted of six semi-automatic 45 mm 21-K AA guns with 600 rounds per gun and four DK machine guns, with 12,500 rounds per gun, but were significantly increased in service. The Project 26bis ships carried nine 21-K mounts and the Project 26bis were built with an additional ten fully automatic 70-K AA guns with a thousand rounds per gun. Over the course of World War II most, if not all, of the 45 mm guns were replaced by 37 mm guns and one or two Lend-Lease quadruple Vickers .50 machine gun MK III mounts were fitted to the ships in the Baltic and Black Seas, although each ship varied in its anti-aircraft suite.Yakubov and Worth, pp. 84, 86-7
Six 39-Yu torpedo tubes were fitted in two triple mountings; these tubes could be individually adjusted to spread out their salvos. Molotov and Kaganovich replaced their launchers with the more-modern 1-N mount during the war. A total of 96 KB or 164 Model 1912 mines could be carried by the first pair of ships. A pair of depth charge racks were mounted as well as four BMB-1 depth charge throwers. Twenty large BB-1 and thirty small BM-1 depth charges were carried although no sonar was fitted for the Project 26 and Project 26bis ships. They did mount the Arktur underwater acoustic communication system. Kalinin and Kaganovich received the Lend-Lease ASDIC-132 system, which the Soviets called Drakon-132, as well as the experimental Soviet Mars-72 sonar system.Yakubov and Worth, p. 88
The Project 26 ships were fitted with the Molniya fire control system for their main guns which included the TsAS-2 mechanical computer and the KDP3-6 director. Each turret and the director had DM-6 rangefinders which allowed multiple targets to be engaged using a combination of local and central fire control. The four later ships had an improved Molniya-ATs fire control system which could accept data from spotter aircraft. The anti-aircraft armament was controlled by the Gorizont-1 system with a SO-26 computer, Gazon vertical gyroscope and a pair of SPN-100 directors on each side of the superstructure. Each director had a fully stabilized rangefinder. Voroshilov had SPN-200 directors, but the Project 26bis ships used the Gorizont-2 system. This had a more advanced Gorizont-2 computer and Shar vertical gyroscope.Yakubov and Worth, p. 87
The first Soviet ship to carry a radar was Molotov which was given a Redut-K air warning system in 1940, which she used for the entire war. Lend-Lease radars equipped most of the other ships. The British Types 281, 291 and the American SG radars were used for air search. Main battery fire control radars were the British Types 284 and 285 while anti-aircraft fire control was provided by the Type 282 radar. Soviet-designed Yupiter-1 and Mars-1 gunnery radars were fitted in Molotov and Kalinin by 1944.
Machinery The ships had a twin-shaft-unit machinery layout with alternating boiler rooms and engine rooms. The machinery for Kirov was shipped from Italy (being diverted from the contract for the ). The machinery for the rest was built in Kharkiv to Italian plans. The Soviet TB-7 geared turbines proved to be more powerful and more economical than the originals. Kirov burned of fuel oil per unit of horsepower compared to Kalinins . Furthermore Kirov produced only on trials while Voroshilov made and was almost a full knot faster. Six license-built Yarrow-Normand type water-tube boilers powered the turbines with a nominal capacity of 106-tonnes/hour of superheated steam at a pressure of and a temperature of . Each shaft drove a three-bladed bronze propeller for a designed speed of , although this varied from ship to ship. The normal oil capacity was between , but the ships varied widely in the amount of oil carried at full load; this ranged from . Endurance figures also varied widely at full load, from at . The maximum amount of fuel that could be carried ranged from .Yakubov and Worth, p. 90
Protection The armour scheme formed a raft around the vitals, protected by a waterline belt, deck and traverse bulkheads uniformly in thickness. The turret and barbette armour was also 50 mm thick. The conning tower sides were with a 100 mm roof. A box protected the steering gear and a number of control positions were protected against splinters: for the torpedo control station, for main-battery fire control and secondary gun shields, for the secondary-battery control position and the auxiliary command station had sides and roof.Yakubov and Worth, p. 89
The belt extended or 64.5% of the ship's length. Its total height was , of which was below the designed waterline. A double bottom extended past the armored traverse bulkheads and a thin longitudinal bulkhead provided some measure of protection against flooding. It has been judged too thin to withstand a torpedo's detonation, but possibly the far-side bulkhead might survive intact, which would cause a list from asymmetrical flooding.
The armor of the Project 26 ships was vulnerable even to destroyer-class weapons at ranges under and the last four ships were given additional armor. The belt, traverse bulkheads, barbettes and turret face thicknesses were all increased to and the box protecting the steering gear was increased to . One oddity of the later ships' armor scheme was the joint between the armour deck and belt. The top and bottom edges of the belt were tapered, the outer surface angling in from the edge to a thickness of 45 mm. Similarly the deck edge was also tapered down to about 25 mm for its outermost 200 mm. It has been speculated that "This seam in the protection, representing a small target area, may simply have served to save weight and simplify construction."Yakubov and Worth, pp. 89-90
Aircraft The Kirovs were designed to carry two aircraft, but German catapults had to be imported. Two Heinkel K-12 catapults were bought in 1937 for Kirov and Voroshilov. They could traverse 360° and launch an aircraft weighing at a speed of , although no suitable aircraft were in service until the KOR-1 seaplane entered service in September 1939. They proved to be unsuitable for rough-weather landings and were disembarked when Operation Barbarossa began. Gorky and Molotov mounted Soviet-built ZK-1 catapults of roughly comparable performance, but were destined never to use them for lack of suitable aircraft.