the tank had a thicker turret casting and the improved two-plane gun stabilization system from the t-54b, as well as night vision fighting equipment. nva and arvn engaged each other with tanks for the first time during operation lam son 719, in february 1971. 1961, a t-55 tank was used to test the "almaz" tv complex, which was supposed to replace the standard observation devices right after a nuclear explosion or while fording a body of water. cuban and soviet sources maintain that they destroyed ten olifant tanks and twelve ratels, while south african and western sources maintain that only one olifant and one ratel were damaged, as well as one ratel being destroyed. the increased cruising range can go up to 715 kilometers with two 200-liter auxiliary fuel tanks which can be carried on the rear. waiting for the nva column to close to between 2,500 and 3,000 meters, the 90-mm guns of the pattons opened fire, quickly destroying nine pt-76 light tanks and two t-54 medium tanks. in october 1954 a t-54a tank, designated as t-54m (ob'yekt 139) served as a testbed for new d-54t and d-54ts 100 mm smoothbore guns and "raduga" and "molniya" stabilization systems, which were later used in the t-62. a marconi fire control system which was originally developed for the american light tank stingray was fitted. abundance and age together make these tanks cheap and easy to purchase., the t-54/55 tanks have been manufactured in the tens of thousands, and many still remain in reserve, or even in front-line use among lower-technology fighting forces. as in most tanks of that generation, the internal ammunition supply is not shielded, increasing the risk that any enemy penetration of the fighting compartment could cause a catastrophic secondary explosion. it was the mainstay of armoured combat units during the yugoslav wars, where it proved vulnerable to infantry equipped with anti-tank rockets, and to misemployment in urban areas and unfriendly terrain. this tank incorporates the tsfc 2-axis gun stabilization, a new type 70 gunner's sight, full active infrared night fighting equipment, and engine smoke discharger, an nbc protective system, and a laser rangefinder.
the main issue was a larger turret ring, which suggested slightly enlarging the hull. to increase the operational range, 300 litres (66 imp gal; 79 us gal) fuel tanks were added to the front of the hull, increasing the overall fuel capacity to 680 litres (150 imp gal; 180 us gal). during the battle, the iranians lost 20 chieftains plus other armoured vehicles and withdrew. soviet tanks were factory-overhauled every 7,000 km and often given minor technology updates. the t-55 tank remained the most common tank in the armies of the yugoslavian successor states until recently, and it was the most used tank by all armies during the wars. one t-55 tank fitted with this gas turbine engine passed trials but was deemed unsatisfactory and the design did not go into production. the 1973 yom kippur war, the t-54a and t-55's gun was starting to lose its competitive effectiveness relative to the 105 mm royal ordnance l7 gun mounted in israeli centurion mk v and m60a1 tanks. the t-62 and the t-55 are now mostly in reserve status, with all russian active-duty military units mainly operating the t-72, the t-80 and the t-90. starting in 1974, t-55 tanks received the ktd-1 or ktd-2 laser rangefinder in an armoured box over the mantlet of the main gun, as well as the r-123 or r-123m radio set. on 9 november 1987, an engagement between south african and angolan tanks occurred when thirteen olifant mk1as eliminated two t-55s in a nine-minute skirmish. the track system was dominated by the five large road wheels with the front most pair set noticeably apart from the remaining four rear sets. t-55 main battle tank was basically the t-54 with a new turret and more powerful engine. improvements over the t-54 include a larger v-12 water-cooled diesel engine with 580 rather than 520 hp, and an increased cruising range of 500 rather than 400 kilometers (600 kilometers with auxiliary tanks).
t-44, an unsatisfactory model, became the t-54 main battle tank when the t-44 chassis was equipped with a new turret and a heavier 100mm main gun. however, the t-54/55's first appearance in the west around the period of the 1950s (then the beginning of the cold war) spurred the united kingdom to develop a new tank gun, the royal ordnance l7, and the united states to develop the m60 patton. in 1970, new and old t-55 tanks had the loader's hatch modified to mount the 12. t-55s again participated in a critical engagement near cuito cuanavale on 14 february 1988, when cuba's 3rd tank battalion counter-attacked to spare angola's 16th brigade virtual annihilation by 61 mechanised infantry battalion group and the 4th south african infantry battalion. in 1959, some tanks received mountings for the pt-55 mineclearing system or the btu/btu-55 plough. while the t-54/55 is not a match for a modern main battle tank, armour and ammunition upgrades can dramatically improve the old vehicle's performance to the point that it cannot be dismissed on the battlefield. advances in armour-piercing and heat ammunition would improve the gun's antitank capabilities in the 1960s and 1980s. the engine compartment and fuel tanks on the shelves over the tracks were armour-protected. due to the lack of a sub-caliber round for the 100 mm gun, and the tank's simple fire-control system, the t-54/55 was forced to rely on heat shaped-charge ammunition to engage tanks at long range well into the 1960s, despite the relative inaccuracy of this ammunition at long ranges. crew accommodations amounted to four personnel to include the driver in the hull and the tank commander, gunner and loader in the turret section. in)) it compared favourably with the is-3, thanks to its improved antitank gun and better mobility. to zaloga, "by the standards of the 1950s, the t-54 was an excellent tank combining lethal firepower, excellent armor protection and good reliability"  while remaining a significantly smaller and lighter tank than its nato contemporaries—the us m48 patton tank and the british centurion tank. the next page for specifications of the t-54/t-55 main battle tank.
t-54/55 and the t-62 were the two most common tanks in soviet inventory—in the mid-1970s the two tank types together comprised approximately 85% of the soviet army's tanks. the czechoslovak version uses a laser rangefinder mounted over the main gun and a wind sensor. all t-55's mount an infrared gunner's searchlight above, and to the right of the main gun.-55a model 1974 this version is equipped with the ktd-2 laser rangefinder, which is mounted immediately above the main gun in an armored box. iran lost 200 chieftain and m60a1 tanks in the battle. the t-54-2 entered production in 1949 at uralvagonzavod, which produced 423 tanks by the end of 1950. 1959, it served as a basis for the t-55k command tank which was equipped with an additional r-112 radio set, an ab-1-p/30 fuel powered accumulator charging unit, and tpn-1-22-11 night vision sight. most of these tanks also received the same improvements of the t-55am2pb. t-55 was the most numerous tank of the yugoslav people's army (jna). in the beginning of the 1960s, the okb-29 design bureau in omsk was working on adapting the tank to use a gtd-3t gas turbine engine developing 700 hp (522 kw). t-54 main battle tank, more heavily gunned than the t-34, was supplied to a large number of military forces around the world. x 100mm d-10 rifled main gun (at-10 "stabber" atgm capability). t-54/55s have been re-armed with improved tank guns, aa machine guns, advanced armour arrays, and technologies, such as laser range finders and computerized fire control systems, that did not exist when the tank was first being built in the early days of the cold war.
the tank was supposed to be equipped with the "rosa" fire protection system.-54 and t-55 tanks continued to be upgraded, refitted, and modernized into the 1990s. the tanks have good mobility thanks to their relatively light weight (which permits easy transport by rail or flatbed truck and allows crossing of lighter bridges), wide tracks (which give lower ground pressure and hence good mobility on soft ground), a good cold-weather start-up system and a snorkel that allows river crossings. ammunition load for the main gun was increased from 34 to 45, with 18 shells stored in so called "wet containers" located in hull fuel tanks (the concept for which came from kartsev's cancelled ob'yekt 140). it was fitted with a new 100 mm d-10t2s tank gun with stp-2 "tsyklon" 2-plane stabilizer. tank was heavily used during the iran–iraq war of 1980-88. 9 april 1972, all three squadrons of the 20th tank regiment fought enemy armour, firing upon tanks accompanied by infantry, again while occupying the high ground. t-55 main battle tank was a further upgrade to the t-54 series appearing in the late 1950s and intended to counter the new american m60 series. the 100mm d-10t tank gun of the t-54 and the t-55 was also more powerful than its western counterparts at that time (the m48 patton was initially equipped with a 90mm tank gun and the centurion was first fitted with a 20-pounder (84mm) tank gun). most of these vehicles were also retrofitted with the same fire-control improvements of the t-55am2pb, including the at-10 stabber antitank guided missile, the volna fcs, as well as the automotive and communications improvements. its development never stopped throughout the second world war and it continued to perform well; however, the designers could not incorporate the latest technologies or major developments as vital tank production could not be interrupted during wartime. advantage lasted until the t-54 began to be countered by newer western developments like the m60 main battle tank and upgraded centurions and m48 pattons using the 105 mm rifled m68 or royal ordnance l7 gun. t-55 was significantly superior to the is-2/is-3/t-10 heavy tanks in many respects, including the rate of fire of the gun (at least four compared to fewer than three rounds per minute).