(Ikv-91 prototype image). In the mid-60s the Swedish Army had a large fleet of armored combat vehicles that after many years of service were beginning to become almost obsolete in some cases. In 1965 the Swedish Ministry of Defense announced a competition to develop a new armored combat vehicle and the companies Bofors, Hägglunds & Söner and Landsverk entered it. In the following months, the 3 firms presented a total of 14 different designs for a “tank destroyer.” Finally, the 3 best designs were selected, of which the one from the Hägglunds firm was the winner, which in the opinion of the Swedish Army was the one that met all the requirements demanded in the program.(Ikv-91 prototype image). The main requirements of the Swedish Army were that the new vehicle had to have excellent mobility, a powerful anti-tank gun and be able to operate in difficult terrain, since it was expected to use this vehicle in the defense of the northern territories of the country, known as Norrland, and which are within the Arctic Circle, where extreme temperatures of up to -35ºC are reached. In April 1968 the firm Hägglunds was awarded with a contract to begin the development of a new vehicle with which to replace some of the most outdated vehicles. This contract included the building of three prototypes and Hägglunds decided to put aside previous concepts and start a new design from scratch, including the most modern technology of the time and of course taking into account that everything had to be manufactured in Sweden to continue respecting the country’s neutrality policy.(Ikv-91 prototype image). Thanks to the experience obtained by Hägglunds in the building of the Pbv-302 APC family and the derived vehicles Bgbv-82 ARV and Brobv-941 AVLB, the development of the new vehicle could be carried out quickly and in December 1969 testing of the first prototype began, under designation “Ikv-91 (Infanterikanonvagn 91)”. In October 1970 the second prototype was delivered, and in December of that same year the third and last one was delivered. The designation “Infanterikanonvagn 91” came from combining the Swedish term used to designate assault guns plus the number 91, which meant that it featured a 90mm gun (9), and it was the first (1) assault gun to carry a weapon of this caliber.The Ikv-91 was an all-welded steel vehicle with a conventional internal layout divided into 3 compartments: the driver at the front, the fighting compartment in the center, and the engine at the rear. Despite being classified as a tank destroyer by the Swedish Army, that is, a defensive vehicle, it was decided to equip this vehicle with a turret to take better advantage of firing positions and to be able to shoot at several targets without having to change position, as normally happened with the turretless tank destroyers of the time.The crew was made up of 4 members, driver, commander, gunner and loader. The driver was at the front of the hull on the left and had its own access hatch. In front of the hatch there were three day periscopes with the possibility of installing periscopes for night driving. The other 3 crew members were inside the turret, the commander and gunner on the right of the gun and the loader on the left. The commander had a small cupola equipped with several M-17 day periscopes and a ×10 periscopic sight in the front. This cupola could rotate 240º independently of the turret using an electric servo motor. The commander and the gunner shared the same hatch but had different vision elements and the loader had his own hatch equipped with a day periscope. On the side of the turret next to the loader there was a hatch through which the used casings were manually ejected.During the design of this tank destroyer, a multitude of details were taken into account to improve crew comfort. For example, all the plates that made up the hull were curved to stiffen them and reduce noise inside. The turret ring was about 2 meters in diameter and the turret was spacious enough for the crew to operate with bulky arctic clothing, something very common in Northern Sweden. Fans with heat exchangers were also installed in the driver and fighting stations to ventilate and heat these spaces. This vehicle did have an NBC protection system using overpressure in the crew compartments. The system consisted of an electric fan installed in the air intake that cleaned the air of particles through a double filter system before it entered the interior.Hägglunds carefully studied the design of the Ikv-91 taking into account that it had to be completely amphibious vehicle, hence the appearance of its front, and although it was a fairly large vehicle, it had a very low silhouette that made it a difficult target to hit. A good part of the automotive components were those of the Bgbv-82 ARV and it had the same undercarriage formed by six dual rubber-tyred roadwheels with the drive sprocket at the rear and the idler at the front, without return rollers. The suspension consisted of torsion bars on each wheel with shock-absorbers at the first and last road wheels. This vehicle carried the new Hägglunds M-70 tracks, much more quieter than older tracks, and had studs and 50mm long conical spikes that were mounted in place of the track rubber pads to improve traction in deep snow.The Ikv-91 tank destroyer was equipped with the 12,000 cc straight six-cylinder turbocharged Volvo-Penta TD-120 A diesel engine of commercial origin that developed 330 hp and was coupled to an Allison HT 740 D automatic transmission with 4 forward and 1 reverse gears. The engine was placed diagonally in the engine compartment to save space. This engine allowed this vehicle to reach a power-to-weight ratio of 20.2 hp per ton, much higher than the tanks of that time. Although the maximum speed was 65 km/h on road and 7 km/h on water, off-road mobility was exceptional. The vehicle had 400 liters of fuel that allowed it a range of 500 km.The engine included a series of equipment that improved its performance, such as a built-in blowtorch to pre-heat the engine and a built-in electric preheater for the combustion air to facilitate starting in extremely cold conditions. In addition, the engine exhaust not only fed the turbocharger but caused a flow of cooling air over the clutch-and-brake steering system through an ejector. Access to the engine was also improved by installing a one piece cover plate that opened using a small hand pump and a hydraulic jack. Thanks to a weight of only 16.3 tons and its 45 cm wide tracks, the Ikv-91 achieved a ground pressure of only 0.49 kg/cm2, half that of a battle tank, which allowed it to operate on snow and soft terrain.The Ikv-91 is completely amphibious and moves in the water using its tracks. This feature was vital for the Swedish Army of the time and like other contemporary Swedish vehicles such as the Pbv-302 APC or the Bgbv-82 ARV, only minimal preparation was necessary before entering the water. You just had to activate the 4 bilge pumps, deploy the trim board located on the glacis plate and raise some low screens that were folded around the air inlets and the exhaust and air outlets and you could navigate lakes and rivers.Despite the large dimensions of the Ikv-91, it was able to maintain a low weight thanks to its careful design and not install thick armor, sacrificing passive protection for mobility. The turret was designed with a very well ballistically profiled front without rear overhang, which produced a slight problem of turret unbalance. The armor was made up of steel plates and the front arc was protected against 20mm armor-piercing rounds, but the rest of the vehicle was only protected against light firearms and artillery splinters. The sides of the hull were built with steel plates of 4 and 8mm thickness, which above the tracks formed a “double skin” with the thickest plate mounted towards the inside forming a kind of spaced armor to improve protection against hollow charge rounds.The main armament was a 90mm, 54 caliber long KV90S73 low pressure rifled gun developed for this vehicle by the Swedish firm Bofors. One of the main reasons why it was decided to install a low-pressure gun was because it has a much lower recoil than conventional guns, which allows it to be installed on light vehicles such as the Ikv-91. In addition, these types of guns emit a much smaller flash when they fire, which makes them difficult for the enemy to detect, and they use lighter and smaller projectiles that allow more ammunition to be carried inside the vehicle.To compensate for the low muzzle velocity of the 90mm rounds, Bofors developed fin-stabilized (FS) HEAT (high-explosive anti-tank) and HE (high-explosive) ammunition that was capable of piercing the frontal armor of main battle tanks. The m/84 Slpsgr HEAT-FS round weighed 10.7 kg, of which 4.5 corresponded to the projectile. It had a muzzle velocity of 825 m/s and had a piezoelectric fuze attached to the shaped charge to cause more damage with the explosion, especially behind the armor. The m/72 Slpsgr HEAT-FS round weighed 12.3 kg, of which 6.7 kg corresponded to the projectile and was used against soft skinned targets and personnel. It had a muzzle velocity of 600 m/s and had a mechanical time fuze.The 90mm gun had no stabilization system and could fire at an elevation angle of −10° to +15°. It had a hidraulically powered system that raised the gun at a rate of 10º/s, while the traverse rate of the turret was 20º/s. The barrel had a smoke evacuator in the middle of its length and a well-trained crew could fire up to 8 rounds per minute. The production Ikv-91 carried 59 90mm rounds, although the prototype carried 68. Of these, 16 rounds were carried in ready racks located next to the loader, 25 on the left side to the rear of the turret and the remaining 18 were stored to the right of the driver station. The Ikv-91 could fire from water, with the water absorbing most of the gun’s recoil.The Ikv-91 was a very effective tank destroyer at its time, since it had a modern fire-control system, something quite unusual in a light vehicle, because at that time they were only installed on main battle tanks. The system was developed by Honeywell and consisted of a Bofors laser rangefinder, a ballistic computer and different sensors. The computer determined the degree of elevation of the gun after having the data referring to the distance of the target, provided automatically by the rangefinder or manually by the commander or guner, to which was added more data entered manually from the trunnion cant sensor, ambient conditions, powder temperatures and cross wind. Once this data was provided, the computer offered the corresponding ballistic solution. In the event that the target was moving and was being tracked by the gunner, additional data was provided on the rate of turret traverse and gun elevation from two sensors.The rangefinder was of “coincidence type” and was coupled to a Jungner Instrument AB monocular TP-1050L periscopic sight, with 10x magnification and 6º field of view. This device was installed in the commander’s rotating cupola, so the commander could acquire a target and determine the distance without having to point the gun at the target. Once the target designation button was pressed by the commander, the turret moved quickly and aligned itself with the gunner’s sights and his own sight. If desired, the electrically powered rotating cupola could counter-rotate while the turret rotated, and this way the commander would not lose sight of the target at any time. Of course, the commander’s cupola could be locked in line with the gun or released and rotated manually.The Ikv-91‘s armament was completed with two 7.62mm ksp m/39 machine guns, one coaxial with the 90mm gun and another installed on a pintle mount next to the gunner’s hatch. The ammunition carried for these machine guns was 4,250 rounds. It also carried two 71mm Bofors Lyran illuminating mortars with 12 grenades, which were carried externally on the left side of the turret, although for firing they were mounted on a mounting located on the roof of the turret a little behind the commander’s and gunner’s hatches. Finally, it also carried 12 smoke grenade dischargers, 6 on each rear side of the turret with 24 smoke grenades.After the testing period, where minor buoyancy problems were detected due to the increase in weight of the final prototype, in March 1972 mass production was approved and the Swedish Army placed an order for 200 Ikv-91 tank destroyers, which it received. the nickname “Järven” (Wolverine). In 1974 the first two pre-production vehicles were delivered to the Army, and finally in 1975 the first production vehicle entered service. Subsequently, during the last stage of production, another 12 more vehicles were ordered, bringing the total of Ikv-91 manufactured to 212. Production lasted from 1975 to 1978, without any more vehicles being manufactured later, because it was not exported to any foreign country.These tank destroyers were distributed among various infantry brigades, which received 12 vehicles each. At the beginning of its entry into service, the Ikv-91 suffered problems with the hydraulic system, which was prone to leaks, for which some military personnel gave it the humorous nickname “Läcklund & Sönder” (Leaks and Advances) in reference to its manufacturer Hägglund & Söner. After solving these initial problems, the Ikv-91 proved to be a reliable and very effective combat vehicle thanks to its advanced fire-control system. Its main mission was to accompany the infantry and protect it from the attack of enemy armor, although its use was also planned as part of mobile defense squadrons with the mission of attacking enemy forces during their advance.During its service, the Ikv-91 did not receive major modernizations or significant changes. As the vehicle lacked equipment for night combat when it entered service, they received night vision googles to alleviate this drawback. In addition, the electronic equipment was being adequately modernized to maintain good combat capability and a thermal sleeve was installed on the gun. The Ikv-91 did not serve as a basis for the development of any other vehicle, although it seems that the chassis was used for the development of some weapons and vehicles, such as the “AMOS” twin 120 mm self-propelled mortar system or a road mineclearing vehicle called “Hurricane”.(Ikv 91-105 prototype image). In 1983, the Indian Army showed interest in the Ikv-91, but they were not satisfied with the 90mm main gun and wanted the vehicle to have a 105mm gun capable of defeating any contemporary battle tank. Due to this interest, Hägglunds developed a program called “Ikv 91-105” armed with a fully stabilized Rheinmetall Rh 105-20 super-low recoil gun. To attach this gun, the turret had to be greatly modified, the total weight of the vehicle rose to 18 tons, and also the amount of 105mm ammunition was reduced to only 32 rounds. Two new hydropropellants were also installed that allowed sailing at a maximum speed of 12 km/h but in general the previous mobility was maintained because the engine output was raised to 380 hp.(Ikv-105 prototype image). After the necessary work, the Ikv 91-105 was sent to India, where it carried out a series of comparative tests with other similarly armed vehicles, but unfortunately the Swedish vehicle did not meet the customer’s expectations and was not purchased. Although this vehicle was offered to other potential clients, including the United States, which tested the vehicle, the Ikv 91-105 was not successful. The Swedish Army did not show any interest in a variant of the Ikv 91-105 designated “Ikv-105” that carried various additional improvements, because update the entire Ikv-91 fleet required providing them with a new turret and major modifications, which represented an unaffordable cost. Furthermore, around this time (mid-80s), it became clear that the Ikv-91 was no longer capable of defeating the newer Soviet main battle tanks, so such an expensive modification did not make sense, so finally the Ikv 91-105 program was canceled in the early 90s.At the end of the 1980s, a project began to build an anti-tank missile carrier (ATMC) on the Ikv-91 chassis. It was basically a matter of removing the turret and installing a TOW missile launcher in its place. The vehicle would carry up to 55 missiles inside the hull and it was intended that it could replace the older ATMCs, but again, it did not arouse the interest of the Swedish military and the project did not go beyond the design phase.The Ikv-91 tank destroyers remained in service until the late 90s, when it was decided to retire them, which was completed in 2002. Budget cuts and the obvious lack of effectiveness of its 90mm gun against modern main battle tanks sealed its fate. It was rumored that Sweden and the Congo had signed an agreement in 2015 for the updating and transfer of 39 Ikv-91s from those stored in reserve, but there is no evidence that this operation was finally completed. What is known is that there are several Ikv-91s in running order distributed throughout different museums in Sweden and the Bovington Tank Museum in England. Others units are statically displayed in public places and other museums, mainly in Sweden.
