M247 Sergeant York

The US Army’s first useful self-propelled anti-aircraft gun mounting was the M19 Gun Motor Carriage based on the chassis of the M24 Chaffee. The turret of this manually operated system, armed with two 40-mm Bofors guns, was later modified and installed on the chassis of the M41 Walker Bulldog light tank to produce the M42 Duster. This was obsolete by the late 1950s on the grounds that it was ineffective against high-speed targets.

The first successor proposed for the M42 was the Sperry Vigilante, which was to have been based on a 37mm rotary six-barrel cannon. The cannon was very powerful and offered a very high rate of fire, but in the late 1950s the US Army decided that no gun-based systems could be adequate and therefore opted for the MIM-46 Mauler with detection and tracking radars and nine surface-to-air missiles on an adapted M113 armoured personnel carrier chassis. This had a wholly automatic fire-control system, but proved to be technically beyond the state of the art for its time, and was therefore cancelled in 1965. As stop-gaps offering modest capability, the US Army then opted for the M163 with the 20-mm six-barrel rotary cannon on an M113 chassis with an optical fire-control system, and the MIM-72 Chaparral with four AIM-9 Sidewinder missiles on a more extensively modified M113 chassis. Both the M163 and MIM-72 were optionally used in conjunction with the MPQ-49 Forward Area Alerting Radar.

Potent low-level air threat

During the late 1960s the combination of the helicopter and the anti-tank missile had improved to the point at which they represented a major threat to armoured forces. This was especially true of attack helicopters, which offered the possibility of loitering near the front behind cover to pop up, acquire a target, launch a missile, and then return to cover as the missile flew to the target. This and other considerations led the US Army to issue a requirement for an Advanced Radar-directed Gun Air Defense System. This offered the reaction speed of the M163 but with the range of the MIM-72, together with a fire-control system combining a forward-looking infra-red sensor and a laser rangefinder for all-weather and night operating capability, on a chassis offering the performance needed to allow the new system to keep up with the latest generation of armoured fighting vehicles in combat. This ARGADS was later renamed the Division Air Defense system.

The Soviet threat was deemed so dangerous at the time that the US Army decided not to follow its traditional step-by-step development and testing process. Instead, it advanced straight into production status by combining a number of off-the-shelf elements in an attempt to knock five years off the design, development and evaluation processes.

The DIVAD plan was revealed to US industries on 18 May 1977, and this called for a system based on the M48 Patton tank chassis, many of which were held in surplus depots. The DIVAD requirement called for the gun to acquire its target and start firing within 5 (later 8) seconds of it becoming visible or coming into its 3,300-yard (3000-m) range, and to possess a 50% chance of hitting a target with a 30-round burst. The system was also to have an all-weather capability and optical aiming capability.

Considerable industrial interest

Several companies responded to the DIVAD contest, and the proposal offered by Ford Aerospace was based on an armament of two 40-mm Bofors 40 mm L/70 cannon mounted in the centre of the turret, a large unit which also carried the separate antennae for long-range search and short-range tracking radars on its top. The antennae were mounted on booms to give them a clear view of the sky, and both could be folded down to reduce the vehicle’s travelling height. The tracking radar was a modified version of the Westinghouse APG-66 from the General Dynamics F-16 Fighting Falcon fighter, and the turret also carried a complete optical sighting and ranging system.

On 13 January 1978 General Dynamics and Ford were each given a development contract for one prototype, the XM246 (two 35-mm Oerlikon KDA cannon) and XM247 respectively, to be delivered in June 1980. Both prototypes were delivered to schedule, and this allowed a comparatively early start on competitive testing and evaluation. The XM247 was selected as superior on 7 May 1981, and given a fixed-price US$6.97 billion development and initial production contract for what now became the M247 Sergeant York.

Advanced feed system

The M247 used an advanced dual linear linkless feed system to load each Bofors cannon. This feed system had upper and lower systems for each cannon, allowing the loading of HE and proximity-fused rounds in separate upper and lower magazines, which carried about 81 and 179 rounds respectively, to allow the firing of pre-programmed bursts deigned to shoot down eight helicopters before reloading was required. Rounds were loaded into the magazine system from the top of the turret, where the opening of a hatch allowed the attachment of a loading rack for the classic four-round stripper clips as rapidly as men could pass them up to the top of the turret. There were four line replaceable magazine units in mirror-imaged left and right components. The system was powered by a hydraulic motor and turned at 75 rpm, which was slow but fed the cannon very reliably.

The XM247 revealed problems almost immediately, most particularly with the tracking radar. This had problems with ground clutter, and in trials could not distinguish between helicopters and trees. Moreover, when the cannon were elevated to a high angle, their barrels projected into the radar’s line of sight and further confused the system. Reaction time was also too low: against hovering helicopters it was 10 to 11 seconds, but against high-speed targets it was 11 to 19 seconds, too long for the system to fire an effective burst.

The prototype’s reliability, availability, maintainability and durability lasted from November 1981 to February 1982, and revealed many operational concerns. The turret traversed too slowly to track fast-moving targets, and had serious problems in cold weather. The simple electronic counter-countermeasures system could be defeated by only minor jamming. The used guns taken from US Army stock had been twisted as a result of careless warehousing. The most unsurprising problem was that the M48 chassis, now 30 years old and carrying the new 20-ton turret, could not readily keep up with the modern tracked vehicles it was designed to protect.

Good money wasted

Despite the development problems and an increasing level of criticism in the US media, the US nonetheless pressed for the deployment of the system – there was no alternative. To add to the M247’s problems, the advent of a new generation of Soviet battlefield helicopter and missiles offered a 6,500-yard (5940-m) engagement range, which was well beyond the M247’s ability to respond successfully. The US the Army announced it was considering the addition of FIM-92 Stinger missiles to the DIVAD system.

At this juncture, Secretary of Defense Caspar Weinberger ordered a series of battlefield-condition tests in 1984. The results were appalling. Unable to hit drones moving even in a straight line, the tests were later relaxed to hovering ones, but the radar proved unable to lock onto even this type of target, as the return was too small, and the testers had to add as many as four radar reflectors to the target before the radar could ‘see’ it. The system could now track the drone, but the following bursts of fire generally managed only to knock the target off course rather than destroy it.

Trials of initial production systems between December 1984 and May 1985 revealed a number of problems, failing 22 of 163 contract requirements, and 22 serious failures in operational readiness, and on 27 August 1985 Weinberger cancelled the programme after some 50 vehicles had been produced.

The details of the three-crew M247 included a weight of  54.4 tons, length of 25 ft 2 in (7.67 m) with the cannon forward and 21 ft 0.75 in (6.42 m) for the hull, width of 11 ft 11 in (3.63 m), height of 11 ft 2.5 in (3.42 m), turret traverse of 360°, cannon elevation between -5° and +85°, rate of fire of 600 rounds per minute with the 33.86-oz (0.96-kg) projectile fired to a maximum range of 13,670 yards (12500 m), maximum ammunition capacity of 580 rounds, powerplant of one 750-hp (559-kW) Continental AVDS-1790-2D water cooled Diesel engine, maximum road speed of 30 mph (48 km/h), and range of 310 miles (500 km).

The Soviet/Russian ZSU-23-4 Shilka self-propelled anti-aircraft mounting

By the mid-1950s, it was clear that the days of the ZSU-57-2 self-propelled anti-aircraft gun mounting were numbered in terms of the system’s operational capability. For all the destructive effect of its large projectiles, the S-68 cannon possessed too low a rate of fire; the poor rates of traverse and elevation made it all but impossible to engage a high-performance manoeuvring target; and the fire-control system limited realistic operational capability to clear-weather daylight operations.

Yet the primary threat faced by the Soviet army was a campaign in Europe against opponents who fielded high-technology weapons including all-weather attack aircraft. What was needed in this tactical scenario was a new air-defence system offering the same levels of battlefield mobility and protection as the ZSU-57-2, but optimised for the short-range protection of Soviet first-line combat formations in all weather conditions by day and night. This called for a tracked chassis carrying a lightweight turret fitted with a multiple battery of fast-firing cannon. The combination of lighter weapons and powerful motors would provide the rapid traverse and elevation rates required for the sustained engagement of high-speed manoeuvring targets, especially when supported by a radar-directed fire-control system for adequate target detection and fast processing of a fire-control solution.

Quadruple cannon mounting

The resulting ZSU-23-4 self-propelled 23-mm quadruple cannon mounting was designed between 1957 and 1962, and was built by the Mytishchy Engineering Works (about 6,500 mountings between 1964 and 1982) for a service debut in 1965 with the Soviet army name Shilka. The replacement of the ZSU-57-2 by the ZSU-23-4 in first-line formations proceeded rapidly, all ZSU-57-2 mountings having been phased out of first-line formations by the early part of the 1970s, and the new equipment soon began to acquire a very considerable reputation when it entered combat in Vietnam and the Middle East. In the latter arena, during the 1973 ‘Yom Kippur War’, many Israeli aircraft succumbed to the Shilka while operating at low levels in an effort to avoid the Soviet-supplied surface-to-air missile such as the 2K12 Kub (NATO designation SA-6 ‘Gainful’) fielded by Egypt and Syria for high- and medium-altitude defence.

In the Soviet army each tank motor rifle regiment had two air-defence companies, in which the previous six ZSU-57-2 systems were replaced by four ZSU-23-4 systems and four 9K31 Strela-1 (SA-9 ‘Gaskin’) or 9K35 Strela-10 (SA-13 ‘Gopher’) self-propelled SAM systems, for short-range defence against low- and very low-level air threats. One organisational step higher, at divisional level, there was an air-defence regiment. Previously this had four batteries each with six towed S-60 57-mm guns in two three-gun platoons, but was now revised with eight ZSU-23-4 mountings in four two-vehicle teams. Eight ZSU-23-4 mountings were also allocated for local air defence to each 2K11 Krug (SA-4 ‘Ganef’) SAM battalion.

Good commonality with other AFVs

The ZSU-23-4 is based on the GM-575 tracked chassis, which uses components of the PT-76 light amphibious tank, and the hull is all but identical with that used for the 2K12 SAM system. The vehicle is divided into three compartments, with the driver’s position at the front left, the fighting compartment in the centre and the power plant at the rear. The core of the fighting compartment is the large rectangular turret, which has an admirably low silhouette. Here are located the other three crew members: the commander on the left under a 360° traverse cupola fitted with three periscopes, with the radar operator/gunner and range operator to his right. These three are separated from the armament section of the turret by a gas-tight bulkhead.

The radar used in the ZSU-23-4 is the RPK-2 Tobol (otherwise 1RL33) known to NATO as the ‘Gun Dish’, which has its downward-folding antenna above the rear of the turret. This J-band radar can detect possible targets at a range of 20000 m (21,875 yards) and track them at 8000 m (8,750 yards). The rest of the fire-control system comprises an optical sight for use when the enemy is using ECM, and a fire-control computer. In typical conditions the ZSU-23-4’s reaction time from target detection to the opening of fire is between 20 and 30 seconds, and estimates indicate that it is 50% more accurate and 66% longer-ranged than the US M163 Vulcan system, which fires smaller projectiles at a somewhat higher rate. The ZSU-23-4 can engage targets while stationary or on the move, with a maximum speed of 25 km/h (15.5 mph) and tilt of 10°, though fire while the vehicle is moving is some 50% less accurate than fire when stationary. The turret can be traversed through 360°, and the cannon can be elevated from -4° to + 85°, high traverse and elevation rates allowing the ZSU-23-4 to engage fast-moving and fast-crossing targets even at short ranges.

Water-cooled cannon

The four water-cooled 23-mm 2A7 (APZ-23 Amur) cannon are stabilised in elevation, and the turret is stabilised in azimuth. Each gas-operated cannon has a cyclic rate of between 800 and 1,000 rounds per minute, translating to a practical rate of between 3,400 rounds per minute with all cannon firing. The cannon fire 190-g (6.70-oz) OFZ HE incendiary and 189-g (6.67-oz) BZR armour-piercing incendiary projectiles, the ammunition generally being loaded as one API and three HEI rounds, with a muzzle velocity of 980 and 970 m (3,215 and 3,182 ft) per second respectively. The BZT projectile can pierce 25 mm (1 in) of armour at 500 m (545 yards), declining to 19.3 mm (0.76 in) at 1000 m (1,095 yards). In general, 3-, 5- or 10-round bursts are fired, though a 30-round burst can also be fired. Access to the weapon compartment at the front of the turret is provided by a pair of roof-located hatches. The maximum range in the surface-to-surface role is 3000 m (3,280 yards), and in the anti-aircraft role the effective slant range is 2500 m (2,735 yards) with an effective ceiling of 1000 m (3,280 ft).

The onboard ammunition capacity is 2,000 rounds in 50-round belts: this provides 520 rounds for each of the upper cannon and 480 rounds for each of the lower cannon. An additional 3,000 rounds of ammunition can be towed in a special limber, though it is more common for each vehicle to be followed, some 1500 to 2500 m (1,640 to 2,735 yards) to the rear, by a supply truck carrying 3,000 rounds.

In typical circumstances, the radar is used for 360° surveillance or sector scan over a limited arc. As soon as an echo is identified as a target by the IFF system, the radar is switched into automatic tracking mode, and starts to feed target data (bearing, elevation and range) into the fire-control computer for the solution of the fire-control problem. As soon as the target is within range, the commander and radar operator/gunner are automatically informed, and the target is engaged. A typical reaction time, from target acquisition to firing, is between 20 and 30 seconds. Naturally enough, the greatest system accuracy follows from the use of all capabilities, but the ZSU-23-4 can also be used in optical mode without the computer and without the stabilisation system, though in either of these modes accuracy is seriously degraded. Standard equipment includes an NBC system and night-vision devices.

Multiple variants

There are at least nine variants of the basic ZSU-23-4, most of them featuring alterations to the cooling and stowage facilities, the latter adding a pannier for two ammunition boxes to each side of the turret. The most important of these variants are the pre-production and initial production ZSU-23-4 of 1965, the full-production ZSU-23-4V of 1968 with enhanced reliability and ZSU-23-4V1 of 1972 with improved radar and an improved engine, and the definitive ZSU-23-4M Beryoza of 1973. This last was produced in three subvariants as the basic ZSU-23-4M armed with modernised 2A7M cannon, the pneumatic loading arrangement replaced by a pyrotechnic loading arrangement, and the welded tubes of the cannon coolant outlet replaced by flexible pipes to increase the cannon barrel life from 3,500 to 4,500 rounds; the ZSU-23-4MZ (Zaproschik or inquirer) of 1977 equipped with the improved Luk IFF system (all ZSU-23-4M mountings were upgraded to the ZSU-23-4MZ standard during scheduled maintenance); and the ZSU-23-4M2 of 1978 as the so-called Afghan war variant for enhanced capability in mountain combat by the replacement of the radar system by a night sight, the ammunition capacity increased from 2,000 to 4,000 rounds. Other change in the ZSU-23-4M mountings included panniers for three rather than two ammunition boxes, an armoured cover for the cannon, an improved radar not slaved to the gun barrels to allow independent radar search, and a digital rather than analog fire-control system that could be linked electronically to off-set radars and fire-control systems. In 1985 there appeared a subvariant of the ZSU-23-4M with revised radar, identifiable by sidelobe clutter-reducing vanes in the centre of the antenna dome, and IFF protrusions on the sides of the antenna dome.

Additional firepower could be added in late modifications by a roof-mounted pod of six 9K38 Igla (SA-18 ‘Grouse’) or side-mounted 9K310 Igla-1 (SA-16 ‘Gimlet’) short-range SAMs.

Further developments have been undertaken by former elements of the USSR, including former bloc countries. Russia and Belarus created the ZSU-23-4M4 and ZSU-23-4M5 modernised variants of 1999 with pairs of 9K38 Igla man-portable air-defence systems on each side of the turret and equipped with 81-mm (3.19-in) smoke grenade launchers, laser emission sensors, optronic vision devices including a TV system for driver, and an improved radar system. Other changes included the replacement of the mechanical transmission by hydrostatic transmission, and mobility increased to the level of main battle tanks.

The Donets of 1999 was a Ukrainian modernisation developed by the Malyshev Tank Factory in Kharkov. It has the modified turret of the ZSU-23-4M, additionally armed with two pairs of Strela-10 SAMs, and a doubled ammunition capacity, on the hull of the T-80UD main battle tank.

The ZSU-23-4MP Biała is a Polish upgrade of 2000 with PZR Grom SAMs and fully digital passive aiming devices instead of the radar.

Many operators

Operators of the Shilka in 2015 include Afghanistan, Algeria, Angola, Armenia, Azerbaijan, Belarus, Bulgaria, Cameroon, Congo, Cuba, Egypt, Ecuador, Ethiopia, Georgia, Guinea-Bissau, Hungary, India, Iran, Iraq, Israel, Jordan, Laos, Lebanon, Libya, Mali, Mongolia, Morocco, Mozambique, Nigeria, North Korea, Peru, Poland, Somalia, Russia, Syria, Turkmenistan, Ukraine, Western Sahara, Vietnam and Yemen, while former operators include East Germany.

The other data for the ZSU-23-4 tracked self-propelled point-defence tactical AA cannon mounting include a weight of 19000 kg (41,887 lb), length of 6.535 m (21 ft 5.25 in), width of 3.125 m (10 ft 3 in), height with the radar lowered 2.576 m (8 ft 5.375 in) and with the radar raised 3.572 m (11 ft 8.67 in), welded steel armour varying in thickness between 10 and 15 mm (0.39 and 0.59 in) in the electrically powered turret, powerplant of one one 209-kW (280-hp) V-6R water-cooled six-cylinder Diesel engine with 515 litres (113.3 Imp gal) of fuel, road speed of 50 km/h (31.1 mph), cross-country speed of 30 km/h (18.6 mph), road range of 450 km (280 miles) and cross-country range of 300 km (186 miles).

The US M16 self-propelled anti-aircraft mounting

The M45 quadruple machine gun mounting was a weapon mounting with four 0.5-in (12.7-mm) Colt-Browning M2HB (heavy barrel) L/90 heavy machine guns in the form of M2 Turret Type weapons mounted in vertical pairs on each side of the gunner’s electrically open cab. The M45 was developed by the W. L. Maxson Corporation in 1942 as successor to the same manufacturer’s current M33 twin mounting. Although designed as a short-range anti-aircraft weapon, the M45 also proved very effective against many types of ground targets including massed infantry, trucks and lightly armoured vehicles. Introduced to service in 1943 and manufactured until 1953, the M45 mounting remained in US service as late as the Vietnam War.

In order to develop a mobile anti-aircraft weapon, several mountings armed with two 0.5-in (12.7-mm) heavy machine guns were evaluated on the open flatbed of the M2 half-track vehicle. These mountings included an offering from Bendix, the Martin aircraft company and Maxson. The last’s M33 mounting was preferred, and so was adapted for installation on the larger M3 half-track vehicle and accepted for service in 1942 as the M13 Multiple Gun Motor Carriage. The mounting was also used on the similar M5 half-track as the M14 Multiple Gun Motor Carriage. The mounting was also tested in 1942 as a replacement for the turret of the M3 light tank, but proceeded no further than the prototype stage.

Even as production of the two multiple gun motor carriage variants was underway, work had commenced on a development which doubled the mounting’s firepower. The revision of the M33 to take four machine guns created the M45 mounting.

A formidable close-range weapon

Together with the 40-mm Bofors gun, the M45 became the principal weapon of the mobile anti-aircraft artillery battalions deployed by the US Army during the WWII the European theatre. It was used primarily for the defence of larger units, especially field artillery, against both air and surface attack. Through a combination of their overall firepower, and the fact that the four machine guns could be harmonised to converge on a variable single point, the M45 units served as a potent deterrent to low-level air attacks. Multi-gun mounts were developed for the M2 machine gun because the weapon’s rate of fire, varying between 450 and 550 rounds per minute, was deemed too low for effective anti-aircraft use.

The M45 was employed until 1945 as a land-based weapon, particularly during the German land offensive in the Ardennes in December 1944/January 1945. Although the Allies had achieved air supremacy by the time of the invasion of Normandy in June 1944, German air attacks were still a threat as fighter-bombers could approach and attack at low altitude and then quickly escape. At Oppenheim, when the Allies were gathering to make a massive push after crossing the Rhine river in March 1945, the German deployed 248 warplanes in an effort to destroy the bridge. However, massed US anti-aircraft artillery battalions shot down 30% of the attacking force, mainly with M45 mountings – preventing the bridge’s destruction.

The M45 was combined with two towed mounts, namely the M20 light single-axle trailer, to create the M55 Machine Gun Trailer Mount. The heavier M17 tandem-axle trailer was based on a searchlight platform to create the M51 Multiple Machine Gun Carriage. These mounts could be towed by any 4×4 light truck. In firing position, the equipment was lifted on three jacks, comprising one at the front and two at the rear of the trailer. This allowed the removal of the two wheels before the mounting was lowered onto the ground to provide a stable firing platform.

Other data for the M55 on a two-wheel trailer included a weight of 2,950 lb (1338 kg) in travelling order and 2,150 lb (975 kg) in firing position, travelling length of 9 ft 5.75 in (2.89 m), travelling width of 10.33 in (2.09 m) and height of 3.25 in (1.61 m) reducing to 4 ft 8 in (1.42 m) in firing position, rate of fire of 500 rounds per minute cyclic and 150 rounds per minute practical for each barrel, and effective horizontal and slant range of 1,650 and 1,300 yards (1510 and 1190 m).

Self-propelled mountings

For greater mobility the M45 could also be mounted semi-permanently on the flatbed of a 6×6 truck. For a superior combination of mobility and cross-country capability, tit could also be mounted on the M3 half-track vehicle to create the M16 Multiple Gun Motor Carriage, and on the M5 half-track vehicle to create the M17 Multiple Gun Motor Carriage.

The M45 mounting was operated by one gunner in a semi-armoured cab, fitted with an M18 reflex sight and two loaders. The mounting could be traversed through 360° and elevated through an arc of 100° between -10° and +90°. The traverse and elevation movements were both electrically driven at the rate of 60° per second, power being provided by two 6-volt batteries which were recharged by a small petrol-powered generator. All four guns could be fired at once, but it was more common for the gunner to alternate between the upper and lower pairs of guns. This allowed the barrels of one pair to cool while the other was in use, and thus opened the way for more extended periods of action as the overheating of the gun barrels was reduced.

Each gun was fed with 210 rounds of belted ammunition from a ‘tombstone’ chest weighing 89 lb (40 kg) fully loaded and fitted on the outer side of each gun. The ammunition types which could be used were AP, API, API-T, ball and incendiary, with a projectile weight between 33.18 and 46.79 g (1.17 and 1.65 oz) fired at a muzzle velocity between 2,815 and 3,400 ft (858 and 1036 m) per second.

There was also a Lysam M55 (Modernised) version of this simple system. Evolved as a kit in Brazil by Lysam Industria e Comercio de Maquinas e Equipamentos, it had modern 12-volt electrics, whose batteries were charged by a 5- or 6-hp (3.73- or 4.47-kW) Montgomery M-226 or M-252 petrol engine. Other improvements aimed to increase reliability and maintainability in modern conditions. The modernised equipment was otherwise similar in capabilities and performance to the original model, though the traverse and elevation rates were significantly improved to more than 90° per second – as required for any real capability against fast-crossing targets. The company also trialled a self-propelled version on the chassis of the Bernardini XIA light tank.

Lysam has also produced a version with a pair of 20-mm Hispano-Suiza HS 404 cannon, each with 160 rounds of ammunition, in place of the four 0.5-in Browning machine guns. In this latter guise the Brazilian development was similar in many respects to the Israeli TCM-20 mounting, itself developed from the M55 with two HS 404 cannon.

The German ‘Wirbelwind’ self-propelled anti-aircraft gun

Despite developing Blitzkrieg tactics, the Germans were as slow as the other early WWII powers in developing self-propelled anti-aircraft artillery. This stemmed in part from the German leadership and armaments industry’s primary concern with the development and manufacture of offensive weapons. Yet it was also a result of their belief that their breakthrough forces could be adequately protected by Luftwaffe fighters from opponents’ close support warplanes.

These ideas may have held a certain validity in the first stages of the war, when German land and air forces reigned supreme. However, they became problematic from 1942 onwards. This was when British fighter-bombers and attack aircraft had at last got the measure of German and Italian forces in North Africa. New generations of Soviet fighter-bombers and attack aircraft, operating under an increasingly effective fighter umbrella, had also started to achieve similar results on the Eastern Front.

At this time, then, Germany’s fighter arm was beginning to suffer heavy losses on both fronts. Its land-based 20-37mm anti-aircraft guns, generally used against ground-attack aircraft, had to be towed. This made it difficult for anti-aircraft units to keep up with Panzer divisions.

One of the first German attempts to create an effective anti-aircraft gun was the Leichte Flakpanzer 38(t) (SdKfz 140).  Mounted on the rear of the chassis of the PzKpfw 38(t), a Czech tank used in some numbers by the Germans, it provided both protection and the same level of mobility as the forces it was designed to protect. However, it had limited overall capability due to its lack of firepower. It was followed by the 2-cm Flakvierling 38 auf Fahrgestell Panzerkampfwagen IV, nicknamed the Möbelwagen (furniture van) because of its boxy quadruple 20-mm cannon mounting (later replaced by a single 37-mm cannon mounting). This was based on a large rectangular fighting compartment about 9 ft (2.75 in) long, 8 ft 8 in (2.65 m) wide and 4 ft 1 in (1.25 m) high, and whole walls could be elevated to the vertical position to create a smaller but very boxy ‘furniture van’ look when closed for movement. This was based on the chassis of the PzKpfw IV battle tank. Entering service in April 1944, it soon proved limited by its lack of protection and the restriction of the cannon to the engagement of aerial but not ground targets.

Four cannon

Attempts to overcome both of these limitations paved the way to the design of the 2-cm Flakvierling 38 auf Flakpanzer IV Wirbelwind (whirlwind). This self-propelled quadruple anti-aircraft gun mounting was also based on the PzKpfw IV tank; in this instance, vehicles which had been returned from the front for major overhaul. The Wirbelwind was schemed as the partner, rather than successor, to the Möbelwagen in both its forms. It had its origins in 1944 in the mind of SS-Hauptsturmführer Karl Wilhelm Krause of the 12th SS Panzer Division ‘Hitlerjugend’.

To create the Flakpanzer IV (2 cm) mit PzFgst Panzer IV/3 Wirbelwind, the PzKpfw IV’s turret was replaced by an open-topped and nine-sided turret which housed a 2 cm Flakvierling 38 mounting with four 20-mm L/112.5 cannon and capable of traverse through 360°. The turret was 6 ft (1.83 m) long, 6 ft 6 in (2,0 m) wide and 3 ft 7 in (1.10 m) high, and while closed-top turret design would have been preferable for the provision of overhead protection for the crew, this was not feasible as a result of the need for the rapid clearance of the considerable volume of noxious gases generated by the firing of the four anti-aircraft cannon.

Production of the Wirbelwind was carried out by the Ostbau Werke at Sagan in Silesia. Combat experience confirmed what was already suspected, that the 20-mm cannon shells was losing its capability in the anti-aircraft role, so a more powerful successor was produced as the Flakpanzer IV (3.7 cm) Ostwind (east wind) with a single 3.7 cm FlaK 43 37-mm cannon.

Limited production

Between 87 and 105 examples of the Wirbelwind were produced between July and November 1944 for issue to the anti-aircraft platoons of Panzer regiments, but as a result of unresolved discrepancies between the recorded production numbers at the Ostbau Werke and the Wehrmacht service records, the exact number will probably never be known.

The turret and gun mounting were hand operated, and the cannon could be elevated from -10° to +90° (the former providing a good capability against ground targets) and sighted via a Flakvisier 38/40 optical sight. The cannon mounting had a cyclic rate of fire of 1,800 rounds per minute declining to a practical 880 rounds per minute. The standard 20-mm shell weighed 0.119 kg (4.2 oz), and was fired at a muzzle velocity of 900 m (2,953 ft) per second for a maximum effective ceiling of 2200 m (7,220 ft). The ammunition supply was 3,200 rounds of HE and armour-piercing in the form of 16 20-round ready-use clips in the turret and 15 boxes of reload ammunition in the hull.

The Wirbelwind had a crew of five (commander/gunner, two loaders, driver and radio operator), the secondary armament was one 7.92-mm (0.312-in) MG34 machine gun in the hull’s vertical front plate to the right of the driver with 1,350 rounds for local defence purposes, the weight was 22176 kg (48,889 lb), and the dimensions included a length of 5.89 m (19 ft 4 in), width of 2.88 m (9 ft 5 in) and height of 2.76 m (9 ft 1 in). The engine was a Maybach HL 120 TR 112 water-cooled V-12 unit supplied with 475 litres (104.5 Imp gal) of petrol and delivering 300 hp (224 kW) via an SSG 77 synchromesh gearbox with one reverse and sox forward speeds. This provided for a maximum road and cross-country speeds of 40 and 24 km/h (25 and 14 mph) respectively, and road and cross-country ranges of 210 and 125 km (130 and 78 miles) respectively.

The hull armour depended on the variant of the PzKpfw IV tank used, down to a minimum 50-mm (2-in) frontal armour thickness, and the turret (comprising eight sets of two identical panels welded together) was largely of 16-mm (0.63-in) armour.

The anti-aircraft cruiser – the US ‘Juneau’ class

The three ‘Juneau’ class light cruisers of the US Navy were built to a modified ‘Oakland’ class design: the ‘Oakland’ class was a four-ship subset of the ‘Atlanta’ class standard. The design of the ‘Juneau’ class reflected the operating service’s experience in the later part of World War II against Japanese attacks by massed aircraft forces including kamikaze machines. The ships had the same dual-purpose main armament of 12 5-in (127-mm) L/38 guns as the ‘Oakland’ class but with a much enhanced secondary dedicated anti-aircraft battery, but the earlier classes’ depth-charge tracks and torpedo tubes were removed as unnecessary under current conditions. This reduced topweight and, together with a redesigned superstructure which also improved the guns arcs of fire, reduced weight and increased stability, which in the two earlier classes had been the subject of considerable criticism.

Operational experience in World War II  soon after the first ships had been commissioned dictated the addition of more guns and larger numbers of men to operate these as well as to improve the manning of other systems, and the loss of Atlanta (CL-51) and original Juneau (CL-52) on 13 November 1942 in the Naval Battle of Guadalcanal revealed weaknesses in the design’s stability and hull integrity. These and other matters were already under investigation, and the Bureau of Ships’ redesign, at much the same time as the modified ‘Cleveland’ and ‘Fargo’ class light cruisers. The redesign had the same main armament as the ‘Oakland’ class ships, which omitted the two twin 5-in (127-mm) wing mountings of the ‘Atlanta’ class in order to reduce topweight while also providing additional deck area for 40-mm and 20-mm light anti-aircraft weapons, but the bridge and superstructure were redesigned with the dual objects of trimming weight and improved fields of vision. Advantage was taken of these topweight reductions and usable deck area additions to add more light anti-aircraft weapons without adverse effects on stability. Other changes were the lowering of the nos 2 and 5 main armament mounts to main deck level and of the nos 3 and 4 mounts to o1 deck level, the omission of the boat crane, the improvement of watertight integrity by removing doors on the lowest decks between bulkheads.

Centreline main armament

The main battery of the ‘Juneau’ class cruisers comprised 12 5-in (127-mm) L/38 dual-purpose guns in six twin mounts disposed in equal numbers fore and aft of the superstructure on the centreline: these guns were well suited to the medium-range anti-aircraft role, but the battery suffered criticism for its lack of anti-ship ‘punch’ by comparison with contemporary light cruisers such as the ‘Cleveland’ class vessels with a main battery of 12 6-in (152.4-mm) L/47 guns in four triple mounts mm. The ‘Juneau’ class was designed with a secondary anti-aircraft armament of 32 Bofors 40-mm anti-aircraft guns in six quadruple and four twin mounts, and 16 20-mm rapid-fire cannon in eight twin mounts. After World War II, it was planned that the ships be upgraded with a secondary battery of 3-in (76.2-mm) L.50 guns in place of the 40-mm weapons, but only Juneau was converted to this standard.

Sensors associated with the weapons included air-search and fire-control radars, as well as two high-angle/low-angle director control towers for the main armament and 10 radar-equipped local directors for the 40-mm cannon.

Reliable and powerful propulsion

The ‘Juneau’ class ships had the same propulsion arrangement as the ‘Atlanta’ class ships, with four 665-psi Babcock & Wilcox boilers supplying steam to two sets of Westinghouse geared turbines delivering 55920 kW) two two shafts, and with this the ships could maintain 33.6 kt.

The ‘Juneau’ class ships had the same protective armour as the ‘Atlanta’ class ships, and this included a 3.75-in (95-mm) main belt, 3.5-in (89-mm) bulkheads, 2-in (51-mm) main deck amidships and lower deck ends, 1- to 1.5-in (25- to 38-mm) turrets and bridge, 1.5-in (38-mm) barbettes, and 3.75-in (95-mm) conning tower.

The class was designed for a complement of 47 officers and 695 men, but the wartime complement was in the order of 820 men.

The other data for the ‘Juneau’ class cruiser included a displacement of 6,000 tons standard and 8,200 full load, length of 541 ft 6 in (165.05 m) overall, beam of 53 ft 3 in (16.23 m), full-load draught of 26 ft 6 in (8.08 m), and up to 1,450 tons (1473 tonnes) of oil for a range of 7,410 miles (11925 km) at 20 kt.

All three ships were built by Federal Shipbuilding at Kearny, and none was completed in time for service in World War II. The lead ship was Juneau (CL-119), which was named after her lost half-sister (CL-52), laid down on 15 September 1944, launched on 15 July 1945 and commissioned on 15 February 1946. Spokane (CL-120) was laid down on 15 November 1944, launched on 22 September 1945 and commissioned on 17 May 1946. Fresno (CL-121) was laid down on 12 February 1945, launched on 5 March 1946 and commissioned on 27 November 1946.

Spokane and Fresno were decommissioned in 1949 and 1950 before the start of the Korean War (1950/53), but Juneau, by this time redesignated as an anti-aircraft light cruiser (CLAA-119), participated in the conflict. On 2 July 1950, Juneau, the British light cruiser Jamaica and the British sloop Black Swan were attacked by a North Korean force of four motor torpedo boats and two motor gunboats, but the firepower of the three allied warships sank three of the torpedo boats and both gunboats near Chumonchin Chan. Juneau was decommissioned in 1955. All three of the ‘Juneau’ class ships were considered for refitting as guided missile cruisers or anti-submarine warfare ships, but were sold for scrap in between 1961 and 1966.

The anti-aircraft cruiser – the British ‘Dido’ class

The ‘Dido’ class of British light anti-aircraft cruisers comprised 11 ships (three built by Cammell Laird, two by Scotts, two by Hawthorn Leslie, and single ships by Fairfield, Stephen, Chatham Dockyard and Portsmouth Dockyard), and there were also five generally similar ships of the ‘Bellona’ class, sometimes considered a sub-class of the ‘Dido’ class. The design of the ‘Dido’ class bore strong evidence of the influence of the ‘Arethusa’ class of conventional light cruisers, of which four had been completed. The first group of three ‘Dido’ class ships was commissioned in 1940, and the second and third groups, of six ships and two ships respectively, were commissioned in 1941/42.

The gun round which the class was designed was the 5.25-in (133.4-mm) QF Mk I, an L/50 dual-purpose weapon of the semi-automatic type. Production totalled 267 guns, and two such guns were fitted in each turret, which was of the same essentially circular shape as created for the secondary armament of the ‘King George V’ class battleships. For a dual-purpose gun, 5.25 in (133.4 mm) was a large calibre, but was selected because it was believed that this calibre would provide the 80-lb (36.3-kg) maximum weight of semi-armour-piercing or HE shell which could still be manually handled by the average gun crew. Unfortunately, the design of the turret was cramped, and the heavy projectile and 41-lb (18.6-kg) filled brass cartridge case resulted in a rate of fire of between seven or eight rounds per minute, which was therefore lower than the expected 10 to 12 rounds per minute. In addition, the slow elevating and training speeds of the mounts were found to be inadequate for the engagement of modern high-speed aircraft.

The Mk II turret weighed between 84 and 96 tons (85.3 and 97.5 tonnes), and could be trained through 150° left and right of the centreline at the rate of 10° per second, and the guns could be elevated between -5° and +70° at the rate of 10° per second. The autofrettaged barrel weighed 1.654 tons (1.681 tonnes) and the semi-automatic breech mechanism 473 lbs (214.5 kg), and the barrel had a typical life of 750 rounds. The gun had a muzzle velocity of 2,600 ft (792 m) per second, and elevated to 45° had a range of 23,400 yards (7130 m) and to 70° a ceiling of 46,500 ft (14175 m). The gun’s capabilities in the anti-aircraft role were greatly enhanced by the 1944 introduction of the VT radar proximity-fused shell.

Problematical turret installation

The A turret in the early ‘Dido’ class cruisers proved prone to jamming, with some 13 incidents being reported in 1940/41. This problem was primarily the result of the light construction methods used on most ships built down to a treaty-mandated weight limit, which allowed the bow to flex in heavy weather or during high-speed turns. The early ships were therefore stiffened in the bow section and received more careful attention to the details of the turret installations. Later ships had these modifications incorporated during their construction and therefore did not suffer from the problem.

The guns and their turrets were difficult to manufacture, and a higher priority was accorded to the completion of the ‘King George V’ class battleships with their full DP batteries. The ‘Dido’ class ships were designed for five turrets (three forward and two aft), but as a result of gun/turret shortages Charybdis and Scylla were completed with eight 4.5-in (114.3-mm) QF Mk III guns in four twin turrets, and three others, including Dido, were completed with only eight 5.25in (133.4-mm) guns in four twin turrets. Dido had her fifth turret installed during a refit late in 1941, Bonaventure was sunk in March 1941 before she could by similarly upgraded, and Phoebe retained the eight-gun armament. The later ‘Bellona’ class was designed from the start with eight guns.

The ships of the first group were also armed with a single 4-in (101.2-mm) QF MK V starshell gun and eight 2-pdr (40-mm) ‘pom-pom’ short-range anti-aircraft guns in two quadruple mountings.

The ships of the second group had the five 5.25-in (133.4-mm) turrets but lacked the 4-in (101.2-mm) gun, and those of the third group had a revised armament, as noted above, with the 4.5-in (113.4-mm) gun which was, in fact, better suited to the primary anti-aircraft role of the ‘Dido’ class cruisers. The 4-in (101.6-mm) gun was also fitted, and the 2-pdr armament was increased to 10 guns.

Sensor and weapon upgrades

During the war the ships were considerably upgraded, often in US yards, with radar and improved short-range anti-aircraft batteries. The radar equipments included Type 272, Type 279, Type 281, Type 284 and Type 285, and the close-range anti-aircraft batteries came to include up to 12 40-mm Bofors guns in three quadruple mountings and 16 20-mm Oerlikon cannon in six twin and four single mountings.

The ‘Dido’ class cruisers saw considerable service and action in World War II, including the Battle of Cape Matapan, the 2nd Battle of Sirte, the Operation ‘Torch’ landings in French North-West Africa, the Operation ‘Overlord’ landings in north-west France, and the Operation ‘Iceberg’ assault on Okinawa, as well as many other duties in the Mediterranean and Pacific theatres. The class lost four of its number (Bonaventure, Charybdis, Hermione and Naiad) in the war, and Scylla was so badly damaged by a mine that she was declared a constructive total loss. The post-war survivors continued in service, and were all decommissioned between 1955 and 1959, and were then broken up.

The other data for the ‘Dido’ class cruiser included six 21-in (533-mm) torpedo tubes in two triple mountings, displacement of between 5,700 and 5,900 tons standard, and 6,900 to 7,600 tons full load, length of 512 ft 0 in (165.06 m) overall, beam of 50 ft 6 in (15.39 m), draught of 16 ft 9 in (5.11 m) increasing later to 18 ft 2 in (5.54 m), 3-in (76-mm) side armour and 1-in (25-mm) bulkheads, four Admiralty-type boilers supplying steam to Parsons geared turbines delivering 62,000 shp (46225 kW) to four shafts for a speed of 32.2 kt, up to 1,100 tons (1123 tonnes) of oil for a range of 1,500 miles (2415 km) at 30 kt or 4,240 miles (6825 km) at 16 kt, and crew of 480 men.

The anti-aircraft cruiser – the US ‘Atlanta’ class

While the ‘Worcester’ class ships with 6-in (152.4-mm) guns can be considered the heavyweights of the anti-aircraft cruiser, they were too late for service in World War II and built only in small numbers. The ‘Atlanta’ class ships with 5-in (127-mm) guns were the middleweights of the type, saw widespread service in World War II and were built in larger numbers.

Intended to serve as destroyer flotilla leaders, four ‘Atlanta’ class light cruisers were authorised during the US Navy’s accelerated build-up in the period before World War II. Armed with 16 5-in (127-mm) L/38 guns in eight twin turrets, the ships had the firepower of three destroyers, and in service operated largely as anti-aircraft platforms, so successfully that the surviving ships were reclassified as CLAA (anti-aircraft light cruiser) vessels in 1949.

The class was schemed as a replacement for the ‘Omaha’ class of the 1920s, and was developed to meet the need for a vessel of light displacement and high speed with the primary mission of combating large-scale attack by aircraft, but the secondary mission of fulfilling other types of light cruiser duty. The ships’ initial purpose was not only that of an anti-aircraft cruiser but that of a small and fast scout cruiser which could operate in conjunction with destroyers on the fringes of the battle line – in addition to operating in the defence of the battle line against destroyer and aircraft attack. While they were not designed to fight successfully against heavier ships, the ‘Atlanta’ class light cruisers were well suited to close surface action in bad weather and/or poor visibility, and also to night actions, in which their fast-firing main guns and eight 21-in (533-mm) torpedoes could be used as an advantage.

British concept

In 1935, an experimental modernisation was carried out by the Royal Navy on two British light cruisers of World War I design origin, Coventry and Curlew. Their main armament of five 6-in (152.4-mm) guns was removed and replaced by an arrangement of 10 4-in (102.4-mm) anti-aircraft weapons in single mounts ‘for use in the Mediterranean as AA escorts’. Considering how little experience then existed to show how important anti-aircraft defence was to a fleet, the idea of a specialised anti-aircraft ship raised a surprising degree of enthusiasm in the Admiralty. At the time a new 5.25-in (133.4-mm) dual-purpose gun was being developed for the new ‘King George V’ class battleship, and a new small cruiser was designed as the ‘Dido’ class, to carry 10 such L/50 guns in five twin turrets on a full-load displacement of about 6,850 tons. The ships’ steam turbines delivered 62,000 shp to four shafts for a speed of more than 32 kt and a range of 4,900 miles (7885 km) at a cruising speed of 16 kt. The design was adapted from that of a more conventional light cruiser type, the ‘Arethusa’ class, whose units were successful as flotilla leaders. The ‘Dido’ class ships were ordered in 1939 and 16 were completed, though construction of the ships outstripped production of the 5.25-in (133.4-mm) guns, so some of the vessels were commissioned with only four turrets (two of them with 4.5-in/114.3-in guns) and others later had one of their turrets removed.

The first four US ships were completed to the baseline ‘Atlanta’ class standard, while the following seven were to the improved ‘Oakland’ subclass standard with slightly different armament as they were further optimised for the anti-aircraft role. With eight 5-in (127-mm) L/38 guns, the four ‘Atlanta’ class ships had by far the heaviest anti-aircraft armament of any cruiser of World War II, and were also the smallest US cruisers of that conflict.

Two lost in action

Of the eight ships completed in World War II (the other three were completed in 1946), two were sunk in action. These were Atlanta and Juneau, both at the Naval Battle of Guadalcanal. The other ships were deactivated comparatively soon after the end of World War II and were scrapped in the 1960s and early 1970s.

As completed, the four initial ships carried a main armament of eight 5-in (127-mm) L/38 dual-purpose guns in four twin mounts: this battery could fire more than 17,600 lb (7983 kg) of shells per minute, the ammunition types including the radar-fused VT anti-aircraft shell which proved so successful in defeating massed Japanese air attacks. Fire control was entrusted to a pair of Mk 37 fire-control systems located on the centreline above the superstructure. As built, the ships lacked radar, but in 1942 Mk 4 fire-direction radar was retrofitted, though from the following year this was replaced by the improved Mk 12/Mk 22 combination.

Problematical secondary armament

The first four ships also possessed an initial secondary anti-aircraft armament of 12 1.1-in (27.9-mm) guns in three quadruple mountings, initially without directors. By early 1942 increased production made its feasible to add a fourth quadruple mount on the quarterdeck, and directors were fitted. However, by a time late in 1942 these troublesome and relatively ineffective weapons were steadily replaced in the surviving ships by the newer and far superior Bofors 40-mm anti-aircraft gun in twin mountings with Mk 51 directors. From a time early in 1942, the close-range anti-aircraft armament was augmented by eight Oerlikon 20-mm rapid-fire cannon in Mk 4 single mountings disposed as two on the forward superstructure, four amidships between the funnels and two on the quarterdeck. From 1943 onward the number of these mounts was increased by the addition of two more on the forward superstructure and a pair on each side of the second funnel to offset the increasing threat of Japanese air attack, especially by kamikaze aircraft. As they became available from a time late in 1943, a quadruple Bofors 40-mm mounting replaced the twin mount on the quarterdeck, the six depth-charge projectors being landed as compensation. However, it should be admitted that the steady addition of radar, more close-range anti-aircraft guns and other equipment seriously impaired the ships’ stability and also resulted in overcrowding as more men had to be added to the ships’ complements to man the additional weapons.

The second group, sometimes known as the ‘Oakland’ class, was commissioned with 12 rather than 16 5-in (127-mm) guns in six six twin mounts and with Bofors guns from the start, with four additional twin Bofors 40-mm mounts by comparison with their predecessors: two displaced the former 5-in (127-mm) wing turrets, which improved the ships’ stability and close-range anti-aircraft firepower while easing congestion, and two between the funnels displacing the previous two pairs of Oerlikon 20-mm cannon. Additionally, the 20-mm battery was increased to a total of 16 such weapons with a pair of them on the bow, four on the forward superstructure, eight amidships as four on each side of the after funnel, and two on the quarterdeck.

By the end of the war, Oakland had been given an anti-kamikaze upgrade: this included the replacement of the four aft Bofors twin mountings with quadruple mountings, and the reduction of the 20-mm mounts to as few as six, though each with twin rather than single cannon. Reduction of topweight was improved by the landing of the two quadruple torpedo tube mountings, which had been the only such mountings on US Navy cruisers commissioned during World War II.

Little used anti-submarine capability

Although the ships had been planned as destroyer flotilla leaders, the original design did not include anti-submarine sensors or armaments such as sonar or a depth-charge battery. Early in 1942, however, the anti-aircraft and radar upgrades were complemented by the addition of sonar and the standard destroyer battery of six depth-charge projectors and two stern-mounted depth-charge tracks. When it was decided that the ships were more valuable as anti-aircraft vessels, the projectors were removed but the tracks were retained. The ships of the ‘Oakland’ subclass were never fitted with the projectors, but were fitted with the two stern tracks.

Search radar was not fitted to the early ships as built, but from spring of 1942 they were refitted with SC-1 and then SG search and Mk 4 radar for fire control. As the war progressed additional and more modern radars were added.

The class was powered by four Babcock & Wilcox boilers supplying steam to two Westinghouse geared turbines delivering 75,000 shp 55920 kW) to two shafts for a sustained maximum speed of 33.6 kt. The bunkers carried 1,360 tons of oil for a range of 9,800 miles (15770 km). Given its role, the ‘Atlanta’ class cruiser was designed with only limited armour protection: 3.75-in (95-mm) belt and bulkheads, and 1.25-in (31-mm) deck, bridge, gunhouses and magazines.

The displacement was 6,718 tons standards and 8,340 tons full load, and the dimensions included an overall length of 541 ft 6 in (165.05 m), beam of 53 ft 2 in (16.21 m) and draught of 20 ft 6 in (6.25 m).

Though originally intended as 26 officers and 523 men, the complement was increased to 35 officers and 638 men in the first four ships, and 45 officers and 766 men in the later ships. All were designed to serve as flagships as they incorporated additional space for a flag officer and his staff, but the additional space was in fact used for the additional crew needed to man the added anti-aircraft weapons and electronics.

Although very formidable as anti-aircraft ships, the ‘Atlanta’ class cruisers did do well in surface combat, the only two ships of the class which did become involved in such combat being sunk: these were two of only three US light cruisers sunk in World War II. Both of the ‘Atlanta’ class ships succumbed to Japanese torpedoes and the gunfire of larger and more heavily armed ships.

Constant top-weight problems

While praised for the number and disposition of its primary anti-aircraft battery, the ‘Atlanta’ class was criticised for its shortage of gunfire directors, which severely limited the capabilities of the primary battery, and also for its early lack of potent secondary and tertiary anti-aircraft batteries. The latter criticism was addressed, though only to an extent in naval shipyards by the end of 1942, but result was that the ships were then top-heavy, which was a problem overcome only in the last three ships (Juneau (ii), Spokane and Fresno), all built by the Federal Shipbuilding and Drydock Company and commissioned between February and November 1946, after the end of World War II.

The ‘Atlanta’ class proper comprised Atlanta, Juneau (i), San Diego and San Juan built in pairs by Federal and the Bethlehem Steel Corporation for commissioning in 1942.  The following four ships, commissioned between December 1942 and February 1945, were Oakland, Reno, Flint and Tucson, all built by Bethlehem.

After World War II, the six surviving ships of the two original subclasses were decommissioned between 1947 and 1949 and placed in reserve. None of the ships was recommissioned to serve in an active role, and all had been stricken by 1966 and then scrapped.

The anti-aircraft cruiser – the US ‘Worcester’ class

The world’s first powered, sustained and controlled aeroplane flight had been made only in 1903 by the Wright brothers. Furthermore, technical developments were made only slowly up to the start of World War I (1914/18),where many pioneers foresaw the emergence of the aeroplane as a weapon. The potential of the aeroplane as a war machine was demonstrated several times in 1910. On 19 January, Lieutenant Paul Beck released sandbags, representing bombs, over Los Angeles from an aeroplane flown by the pioneer aviator Louis Paulhan, and on 30 June Glenn H. Curtiss dropped dummy bombs from a height of 50 ft (15 m) in an area marked by buoys representing a battleship on Lake Keuka. The feasibility of discharging firearms from an aircraft was also revealed on 20 August, when Lieutenant Jacob Earl Fickel of the US Army fired a rifle from a Curtiss biplane at a ground target at Sheepshead Bay, New York. More significantly in terms of future development, a German named August Euler had filed a patent some weeks earlier for a device enabling a fixed machine gun to be fired from an aeroplane.

In 1911 the first HE bombs and the first torpedo were dropped from aircraft. On 11 October of the same year the Italians made the first use of aircraft in war in the Turco-Italian war, initially for reconnaissance and then for light bomb drops. On 2 June 1912, the first aerial machine gun trials began, when Captain Charles de Forest Chandler of the US Army Signal Corps fired a Lewis machine gun from a Wright biplane flown by Lieutenant de Witt Milling.

In World War I the main air threat to warships was initially believed to be the airship, which by this time could carry a substantial weight of bombs. However, the aeroplane steadily came to the fore as the platform from which bombs or torpedoes could be released. This led during the war to the addition of limited anti-aircraft armament to larger warships: the British ‘Caroline’ class light cruisers each carried one 13-pdr (3-in/76.2-mm) high-angle gun, while the ‘Cavendish’ class heavy cruisers carried four such weapons.

The threat of the aeroplane to the warship matured in the period between the world wars. This was reflected in the adoption of heavier-calibre primary anti-aircraft guns intended to tackle higher-altitude aircraft, as well as in the number of smaller-calibre weapons, to put up what was fondly believed would be a ‘wall of fire’ through which no aeroplane could penetrate for a low-level attack. The British ‘Exeter’ class heavy cruiser, for example, carried four 4-in (101.6-mm) guns and two 2-pdr ‘pom-pom’ multi-barrel weapons.

Rapidly developing threat

What no one had adequately appreciated was the advent of the dive-bomber. These carried a point-accuracy bombing capability that could help supplement the area bombing efforts of the higher-altitude bombers and the point-accuracy capability of the low-level bomber armed with torpedoes. The capabilities of all three aircraft types improved as the war progressed, and all available deck area on existing ships was gradually filled with a mass of weapons in the calibres between 20 and 40 mm to tackle low-level attackers.

Another option was the development of cruiser class with a true dual-role capability against air and surface targets. Their main guns could be elevated to high angles of fire against aircraft. They were installed in fast-traversing turrets able to follow their high-velocity targets in two dimensions with the aid of increasingly sophisticated radar and optical fire-control systems. Among the first of this new breed were the British ‘Dido’ class light cruisers, in which the main armament comprised 10 5.25-in (133.4-mm) high-velocity guns in five twin turrets, as well as two quadruple ‘pom-pom’ mountings.

The theatre in which air attack became predominant, however, was that in the Pacific where the US navy battled with the Imperial Japanese navy. The Japanese had initially believed in the winning of the naval war in a climactic engagement between the Japanese and US surface fleets. However, as Japan’s aircraft carrier strength was decimated and the US forces moved closer to the Japanese bases, what transpired was the Japanese expenditure of vast numbers of aircraft in level bombing, dive-bombing, torpedo attack and kamikaze suicide attacks.

The US Navy had a good medium-calibre dual-purpose weapon in its 5-in (127-mm) L/38 gun fitted in single or twin mountings in most ships. To this they added vast numbers of 20-mm and 40-mm cannon in single, twin and quadruple mountings. The combination of these three weapon types allowed US task forces, task groups and task unit to generate huge volumes of fire at every reasonable altitude between the zenith and sea level.

Even so, there were calls for a class of light (yet substantial) cruisers with large-calibre main armaments able to engage air as well as surface targets.

Last throw of the dice

The result was the ‘Worcester’ class of light cruisers. These were based on what was functionally enlarged designs of the ‘Atlanta’ class, but carrying a new 6-in (152-mm) dual-purpose gun – the first gun of this calibre able to undertake the effective engagement of aircraft. Originally planned as repeats of the closely related ‘Cleveland’ and ‘Fargo’ classes, the ‘Wichita’ class ships emerged as considerably longer and heavier.

Worcester was formally started as a project by the Bureau of Ships when a request for designs was made by the General Board on 13 May 1942. The design process resulted in the proposal of no fewer than 10 different design schemes, and the final design differed from the tenth design scheme’s sketches.

The ‘Worcester’ class design was intended to fulfil several operational requirements. It was designed to combine the destroyer’s speed and manoeuvrability with the cruiser’s size and firepower, making it capable of handling air as well as surface surface targets. The design embodied many of the lessons learned during Word War II, as hard-hitting dual-purpose cruisers able to undertake scouting operations and lead a flotilla of destroyers, and also able to keep the sea in almost any weather. The design provided the fuel bunkerage for long deployments, armour protection against gun fire, and a main armament capable of out-reaching and out-hitting Japan’s cruisers as well as repelling massed air attacks.

Massive ‘light’ cruiser

The concept of the anti-aircraft cruiser had evolved swiftly in World War II. The new 6-in (152-mm) L/47 automatic gun was inspired primarily by the need for a longer-ranged anti-aircraft gun, capable of firing a heavy projectile able to defeat heavy land-based bombers and even the first generation of anti-ship missiles. The Bureau of Ships therefore created a new anti-aircraft cruiser around this high-angle gun. The new cruiser proved to be considerably larger and heavier than its predecessor: the ‘Cleveland’ class ships had an overall length of 610 ft 1 in (185.95 m), beam of 66 ft 4 in (20.22 m) and standard displacement of 11,744 tons with a crew of 1,285 men, but the ‘Worcester’ class ships had an overall length of 679 ft 6 in (206.2 m), beam of 70 ft 8 in (21.54 m) and standard displacement of 14,700 tons with a crew of 1,401 men. Because of the greater size of the twin-gun turrets and the increased protection and sturdier construction – with the latter two reflecting the lessons of combat experience – the new ships had a full-load displacement of 17,997 tons. However, the installed power was increased by only 20% to 120,000 shp (89472 kW) delivered to four shafts by four sets of General Electric steam turbines receiving their steam from four Babcock & Wilcox or Westinghouse boilers, so the maximum speed was only 0.5 kt greater than the ‘Cleveland’ class’s 32.5 kt at a time when the intended speed was closer to the 38 kt attainable by the contemporary ‘Fletcher’ class fleet destroyer. This also meant that the ‘Worcester’ class cruiser was no faster than the ‘Essex’ and ‘Midway’ class fleet carriers it was designed to protect.

The main battery consisted of 12 6-in (152-mm) L/47 Mk 16 dual-purpose guns in six two-gun centreline turrets (three forward and three aft) controlled with the aid of four high-angle director control towers disposed in the lozenge arrangement which experience had revealed to by ideal for the control of large numbers of anti-aircraft weapons fighting attackers from any quarter. There was no secondary battery as the six twin main armament turrets were of the dual-purpose type, and this greatly simplified the fire direction task. At commissioning in June 1948, Worcester’s 3-in (76.2-mm) L/50 Mk 27 secondary guns were not installed (six 20-mm mounts were installed for gunnery practice during the shakedown cruise), but these guns were installed early in 1949 and the 20-mm mounts were removed: there were five 3-in (76.2-mm) Mk 27 twin mounts on each beam and one the bow, and two single Mk 33 weapons were fitted on blisters on each side of the stern for a total of 24 3-in (76.2-mm) guns.

At her commissioning, Worcester carried single SR-2, SR-6, SG-6 and SP-1 radars, the SR-2 and SG-6 equipments on the main mast, the SR-6 on a mast just forward of the rear stack, and the SP-1 on the after mast. The SR-2 proved to be inadequate, and was later replaced by the SR-6 from the mast ahead of the after stack, which was in turn removed. The fire-control radars were two Mk 13, four Mk 25, four Mk 35 and six Mk 27 equipments mounted in each of the 6 main turrets. There were also individual radars on the bow and stern 3-in (76.2-mm) gun mounts for a total of 19 fire-control radars.

Protection was based on a 5- to 3-in (127- to 76-mm) belt, 3.5-in (89-mm) armour deck, 1-in (25-mm) weather deck, 4-in (102-mm) bulkheads, 5-in (127-mm) barbettes, 6.5-in (165-mm) turret faces, 4-in (102-mm) turret roofs, 2- to 3-in (51- to 76-mm) turret sides and rears, and 4.5-in (114-mm) conning tower

Disappearing role

The original plan was for 10 ships of the ‘Worcester’ class to be built by New York Shipbuilding, but only two were laid down in World War II as Worcester on 29 January 1945 and Roanoke on 15 May in May 1945. The remaining eight ships were cancelled in March 1945, considered superfluous at a time when World War II was clearly drawing to a close.

Worcester was launched in 4 February 1947 and commissioned on 25 June 1948, while Roanoke was launched on 16 June 1947 and commissioned on 4 April 1949. Both ships served only to December and October 1958 respectively before being placed in reserve and eventually stricken in December 1970 and February 1972.

The gun-armed anti-aircraft cruiser was by this time seen as a dead-end in cruiser design, and so these two revolutionary warships never had a chance to prove themselves in their intended role. The large-calibre automatic gun turned out to be unreliable, and as aircraft speeds increased and as smaller and more agile fighter-bombers became more common, it became obvious that missiles or smaller-calibre guns offered greater potential for the defence of a task force against air attack.

Too late for the war for which they were intended, the ‘Worcester’ class cruisers were obsolete at the time they were commissioned, and were not much liked because of their ‘wetness’, resulting from the low freeboard which represented an attempt to reduce the ships’ great bulk. Unlike the three heavy cruisers of the ‘Des Moines’ class, the two ‘Worcester’ class light cruisers find a second career to prolong their useful lives.

The Soviet IS Series (Part 2)

There were two different Soviet tanks with the IS-4 designation. One of these was the Object 245, which was an IS-2 revised with a long-barrel 100-mm (3.94-in) D-10T gun. The other was a new vehicle projected in parallel with the IS-3 (Object 703) by the same LKZ design and development bureau. For this second iteration of the IS-4 designation, the hull of the IS-2 was lengthened, an additional set of road wheels being added, and an improved engine was installed. The armour of the hull and turret armour was also increased and, after several alternative armaments had been considered, the IS-2’s original 122-mm (4.8-in) gun was retained. Efforts were also made to exploit technical features derived from study of the German Panther battle tank of the World War II period, and this influenced the configuration of the second IS-4’s engine cooling system. The tank was approved for  production from 1947 to 1949, but the type proved to have speed and mobility levels which were considered to be disappointing, so only 250 of the vehicles were built. Most of these were deployed to eastern Siberia in reflection of the fact that they were considered to be lacking in capability for possible service against the Western allies. The tanks had only comparatively short service careers after production ended in 1949.

Yet again, there were two different tanks with the designation IS-6, which was the model number which followed the IS-4. The Object 253 was characterised by the USSR’s attempt to develop a practical electrical transmission system for heavy tanks. Similar systems had been tested previously in France and the USA, and had been used with some success in the German Elefant (otherwise Ferdinand) heavy tank destroyer in World War II. The experimental transmission proved itself to be unreliable, and was also dangerously prone to overheating, so development was soon discontinued. The alternative Object 252 shared the same hull and turret as the Object 253, but had a different suspension arrangement without track-return rollers, and its engine drove a conventional transmission of the mechanical type. The Object 252 design offered no significant advantages over the IS-2, and thus the entire IS-6 project was terminated.

Too weighty

The five-crew IS-7 heavy tank was developed in 1948 and built to the extent of three prototypes. Turning the scales at 149,912 lb (68000 kg), possessing thick armour, and armed with a 130-mm (5.12-in) S-70 L/58.5 stabilised naval gun, the IS-7 was the largest and heaviest of the tanks of the IS series. Despite its weight, the tank proved easy to drive as it was fitted with a number of hydraulic assistance elements. Loaders also noted with approval that the IS-7 was comfortable and that the autoloader was easy to use and provided a rate of fire of eights rounds per minute. The tank was also capable of 37 mph (60 km/h) as it had an engine rated at 1,050 hp (783 kW), and this provided a power/weight ratio which was better than those of most medium tanks of the period. The armour was tested under operational conditions, and revealed itself to be immune to the projectile of the Jagdtiger tank destroyer’s 128-mm (5.04-in) PaK 44 L/55 gun, and also proof against the projectile of its own type of 130-mm (5.12-in) gun. For reasons unknown, most probably the political moves against the ‘Leningrad bosses’ of the same year, but also possibly due to the mobility issues attendant on its weight, the IS-7 did not enter production. Clearly, the IS-7 was able to use few bridges and very little in the way of rail transport, and no Soviet (and indeed Russian) tank accepted for service after this time massed more than 121,252 lb (55000 kg).

The IS-10 was also known as the Object 730, and was the final development of the KV and IS tank series. It was accepted into service in 1952, and in the revised political climate following the death of Iosif Stalin in 1953, it was redesignated as the T-10.

The most significant changes between the T-10 and its direct ancestor, the IS-3, were the later tank’s lengthened hull; seven rather than six pairs of road wheels; an enlarged turret mounting a new gun fitted with a fume extractor; an improved Diesel engine; and thicker protective armour. The general performance of the two types was similar, although the T-10 could carry more ammunition. Like the earlier types which it replaced, the T-10 was deployed in independent tank regiments allocated to armies, and independent tank battalions allocated to divisions. These independent tank units could be attached to mechanised units for the support of infantry operations and to achieve breakthroughs. The T-10 was the final Soviet heavy tank to enter service, and was replaced in first-line formations by the T-64 main battle tank when this became available.

Heavyweight combat tasking

The IS-2 entered combat early in 1944, when the type was assigned to separate heavy tank regiments, each usually of 21 tanks. These regiments were used to reinforce the forces of the most important attack sectors during major offensive operations, and were used tactically as breakthrough tanks. The role of the IS-2 was therefore the support of assault infantry, using its main gun to tackle German bunkers, fortified buildings, emplaced crew-served weapons, and other softer targets. However, the IS-2 was also able to engage any type of German armoured fighting vehicle if needed. Once a breakthrough had been achieved, the IS-2 was replaced by the lighter and more mobile T-34 medium tank for the exploitation phase of the operation.

By the 1950s the emergence of the main battle tank, which combined in a single vehicle the mobility of the medium tank and the firepower and protection of the heavy tank, left the heavy tank effectively obsolete in the Soviet operational doctrine of the period. In the late 1960s what was still left of the Soviet heavy tank force was transferred to reserve service and thence largely to storage.

Other nations which received tanks of the IS series were China (60 IS-2 tanks operated during the Korean War and in concrete bunkers along the Sino-Soviet border), Cuba (41 IS-2M tanks delivered in 1960), Czechoslovakia (eight IS-2 and IS-2M tanks in service between 1945 and 1960; and two IS-3 tanks delivered in 1949 used only for trials), Egypt (unknown number of IS-3M tanks used between 1956 and 1973), Israel (unknown number of IS-3M tanks captured from Egypt in 1967), North Korea (small number of IS-2 tanks), Poland (about 70 IS-2 tanks used in combat between 1944 and 1945; 180 IS-2 tanks survived in 1955, and remained in declining service until the 1960s, some then being converted to armoured recovery vehicle standard), Romania (about five IS-3 tanks) and South Ossetia (limited number of IS-2, IS-3 and T-10 tanks operated to 1995).

The data for the IS-2 in its 1944 initial variant, included a crew of four, weight of 191,411 lb (46000 kg), length of 32 ft 5.75 in (9.90 m), width of 10 ft 1.67 in (3.09 m), height of 8 ft 7.33 in (2.93 m), armour between 30 and 120 mm (1.18 and 4.72 in) thick, main armament of one 122-mm (4.8-in) D-25T gun with 28 rounds, secondary armament of one 12.7-mm (0.5-in) and three 7.72-mm (0.3-in) machine guns, powerplant of one V-2 water-cooled V-12 Diesel engine rated at 600 hp (447.5 kW) and provided with 180 Imp gal (820 litres) of fuel, speed of 23 mph (37 km/h) and range of 150 miles (240 km).

The Soviet IS Series (Part 1)

The designation Iosif Stalin was used for a series of Soviet heavy tanks developed as a successor to the KV series in World War II, and was created under the leadership of Zh. Kotin and N. Dukhov to provide the Soviet forces with a very heavy tank able to survive the fire of the German 88-mm (3.465-in) PaK 43 anti-tank gun and related weapons, and to carry a main gun firing a projectile able to defeat the German Panther battle and Tiger heavy tanks. However, the IS was intended not primarily as an anti-tank vehicle but as a breakthrough tank whose main gun could fire a heavy HE shell in attacks on prepared defences and bunkers.

In the first years of the ‘Great Patriotic War’ with Germany, crews of the KV-1 approved of the tank’s protection but criticised its poor mobility and its lack of a primary armament heavier than the 76.2-mm (3-in) gun of the T-34/76 medium tank. As far as the Soviet leadership was concerned, the KV-1 was also considerably more expensive than the T-34 to manufacture, but without offering greater combat performance. This dissatisfaction was reflected in the Soviet leadership’s decision that some of the KV-1 assembly lines should change to production of the T-34 production. In 1942 the KV-1’s limitations were reduced by the introduction  of the lighter and faster KV-1S tank, though this type was itself gradually superseded in production by the SU-152 self-propelled 152-mm (6-in) gun and disappeared from production in April 1943.

The capture of a Tiger heavy tank in January 1943 persuaded the Soviets to order the development of a new heavy tank, initially designated Object 237. As a result of the extremely fierce armoured warfare in the summer of 1943, which included the climactic Battle of Kursk, Dukhov’s team was ordered to create an interim upgraded version of the KV tank as the KV-85 with an 85-mm (3.35-in) gun derived from the 52-K weapon of the SU-85. The derived weapon was the D-5T, and this fired a projectile able to pierce the armour of a Tiger I tank at a range of 1,095 yards (1000 m). The KV-85 was in fact a modified KV-1S hull carrying the Object 237 turret. The revised armament required an increase in the diameter of the turret ring though the addition of lateral fillets on the hull; the radio operator was omitted so that his position could be used for the insertion of a rack for the larger 85-mm (3.35-in) ammunition; and the hull-mounted machine gun was transferred to the opposite side of the driver position and fixed for operation by the driver.

Before the end of 1943, therefore, the Soviets were able to produce a heavy tank as well armed as the Tiger I. There was a short production run of 148 KV-85 tanks, which made their combat debut in September 1943, and production ended in December of the same year.

Initial iteration

The Object 237 prototype, evolved from the cancelled KV-13, had meanwhile been accepted for production as the IS-85 heavy tank, with deliveries and combat service starting in October 1943. Production lasted only to January 1944, and the designation was simplified to IS-1 after the introduction of the IS-122, which was itself redesignated as the IS-2.

The IS-122 (later IS-2) was essentially a development of the IS-85 (IS-1) with a much larger-calibre main gun. The two options for this weapon were the 122-mm (4.8-in) A-19 and 100-mm (3.94-in) BS-3 guns. The latter offered superior armour-penetrating capability (185 mm/7.28 in compared with 160 mm/6.3 in), but fired a less effective HE round. The BS-3 was also a relatively new weapon and therefore in limited supply, while there was excess production capacity for the A-19 and its ammunition. Compared to the older 76.2-mm (3-in) F-34 tank gun, the A-19 generated far greater muzzle energy and had possessed an accuracy similar to that of the 88-mm (3.465-in) gun of the Tiger Ausf B.

After they had evaluated the A-19 and BS-3 guns, the Soviets selected the former as the D-25 main armament of the new tank, primarily because of its ready availability and the capability of its HE shell against German fortifications. On the debit side, however, the A-19’s use of separate-loading ammunition resulted in a lower rate of fire and a reduced ammunition capacity, which were both  disadvantages in tank-versus-tank engagements. The gun was very powerful, and while its 122-mm armour-piercing shell had a lower muzzle velocity than late-issue German 75-mm (2.95-in) L/70 and 88-mm (3.465-in) L/71 guns, Soviet trials established that the D-25T could penetrate the front armour of the Panther tank at 2,735 yards (2500 m), and was therefore adequate in the anti-tank role.

Ammunition: both weighty and bulky

The worst aspect of the D-25 was its low rate of fire as a result of the weight and size of the two components of its separate-loading ammunition. Initially the rate of fire was between 1 and 1.5 rounds per minute, but modernisation and the replacement of the original manually operated screw breech by a semi-automatic drop breech increased the rate to between 2 and 3 rounds per minute or perhaps slightly more. Another limitation imposed by the bulk of the ammunition was that only 28 rounds (eight armour-piercing and 20 HE) could be carried.

The IS-122 prototype was selected as the basis for a heavy tank to replace the IS-85, and entered production as the IS-2. This was slightly lighter and therefore faster than the heaviest KV Model 1942, had thicker front armour and carried a turret of much-improved design. The fact that the new tank could carry armour thicker than that of the KV series, while remaining lighter, resulted from the improved layout of the armour envelope. The KV’s armour was less well-shaped and featured heavy armour even on its rear, while the IS series concentrated its armour at the front. The IS-2 weighed slightly less than the Panther and was considerably lighter than the tanks of the Tiger series. and presented a slightly lower target than the German types.

Western observers tended to criticize Soviet tanks for their lack of finish and crude construction. The Soviets responded that it was warranted considering the need for wartime expediency and the typically short battlefield life of their tanks.

Early examples of the IS-2 can be identified by the stepped front hull casting and a small, opening driver’s visor. The early tanks lacked main armament travel locks or anti-aircraft machine guns, and had a narrow mantlet. The later IS-2 Model 1944 had an upgraded D-25T gun which could be loaded more rapidly, had a double-baffle muzzle brake, and was fired with the aid of a superior fire-control arrangement. The stepped hull front was replaced with a single plate 120 mm (4.72 in) thick and angled at 60°. Other minor upgrades included the addition of a travel lock on the hull rear, a wider mantlet and, on very late models, an anti-aircraft machine gun.

Some sources identify this as the IS-2m, but it is distinct from the IS-2M, which was a modernised version of the 1950s with fittings such as external fuel tanks on the rear rather than the sides of the hull as on the basic IS-2, stowage bins on both sides of the hull, and protective skirting along the upper part of the track runs.

Two IS-3 models

There are two tanks known as the IS-3. The IS-3 (Object 244) was the IS-2 rearmed with the D-5T-85-BM 85-mm (3.35-in) long-barrel gun: developed by LKZ in Leningrad, this was not accepted for service.

The IS-3 (Object 703) was developed late in 1944 by ChTZ in Chelyabinsk for service from mid-1945. This introduced an enhanced armour layout and a semi-hemispherical cast turret design which became a characteristic feature of post-war Soviet tanks. This lower-silhouette turret provided better ballistic protection, but also reduced the working headroom significantly, especially for the loader, and also limited the maximum depression of the main gun as the gun breech had little room inside the turret to pivot on its horizontal axis. A major tactical limitation resulting from this was that the IS-3 was less able to take advantage of hull-down positions than Western tanks. The IS-3 weighed slightly less than the IS-2 and was 0.30 m (1 ft) lower.

From 1960, the IS-3 was upgraded slightly to the IS-3M in a manner similar to that of the IS-2M.