It introduced advanced features including composite armour, a compact engine and transmission, and a smoothbore 125-mm gun equipped with an autoloader to allow the crew to be reduced to three so the tank could be smaller and lighter.

While it was believed that the T-64 was reserved for elite units, it was also used by much lower level "non-ready formations", for example, the Odessa Military District's 14th Army.

An improved cooling system and a new lightweight suspension was fitted, featuring hollow metallic wheels of a small diameter and caterpillar tracks with rubber joints.

As it did not present a clear superiority in combat characteristics when compared to the T-55, which was entering active service, Morozov decided that production was not yet ready given the project's drawbacks.

This was a potentially risky decision to replace the human loader by an electro-hydraulic automatic system, since the technology was new to Russian designers.

The arrival of the British 105 mm L7 gun and the US M68 variant of it, fitted to the Centurion and M60 tanks, forced the team to adopt composite armour.

Even as the first T-64s were rolling off the assembly lines, the design team was working on a new version, named Object 434, which would allow it to maintain firepower superiority.

The larger size of the 125 mm ammunition meant that less could be carried inside the T-64, and with a fourth crewman loader taking up space as well, the tank would only have a 25-round capacity.

This was unacceptably low for the Soviet designers, but strict dimensional parameters forbade them from enlarging the tank to increase interior space.

Night driving was also supported with the new TPN-1-43A periscope, which would benefit from the illumination of an infrared L2G projector, fitted on the left side of the gun.

The shielding was improved, with fibreglass replacing the aluminium alloy in the armour, and small spring-mounted plates fitted along the mudguards (known as the gill skirt), to cover the top of the suspension and the side tanks.

After three years in service, a first modernisation occurred, comprising: A derived version appeared at the same time, designed for the commanding officer and named T-64AK.

It comprised a R-130M radio with a 10 m telescopic antenna, which could be used only in a static position as it required shrouds, an artillery aiming circle PAB-2AM and TNA-3 navigation station; all of these could be powered by an auxiliary petrol generator.

The majority of T-64As were further modernised after 1981, by mounting a six smoke grenade-launcher 81 mm 902A on each side of the gun, and by replacing the gill plates by a rubber skirt for a longer life.

The T-64A-2M study in 1973, with its more powerful engine and its reinforced turret, served as a basis for two projects: For the latter, the order was given to start its production under the name T-64B, as well as a derived version (which shared 95% of its components), the Object 437, without the missile guidance system for cost reasons.

On 3 September 1976, the T-64B and the T-64B1 were accepted for service, featuring the improved D-81Tm gun (2A46-2) with a 2E26M stabiliser, a 6ETs40 loader and a 1A33 fire control, including: Its ford capacity reaches 1.8 m without equipment.

[10] Two different upgrade packages were developed in 1999:[11] The two variants are also protected by Kontakt-5 modular reactive armour, able to resist kinetic energy projectiles, as opposed to the first models which were efficient only against high-explosive anti-tank (HEAT) shaped charge ammunition.

The Bulat weighs 45 tonnes (44 long tons), and with its 850 hp (630 kW) 5TDFM multi-fuel diesel engine can travel at 70 km/h (43 mph), with a range of 385 km (239 mi).

In 2019, Ukroboronprom reported that the Kharkiv Armoured Plant (KhBTZ) had delivered over 100 updated tanks to the Ukrainian Armed Forces.

[17] The upgraded tanks included new thermal imaging for all crew, remove Luna infrared searchlight, include TPN-1-TPV Ukrainian night sight in place of TPN1-49-23, Nizh reactive armour modules designed for bolt-on replacement on T-64BV turrets, SN-4215 networked satellite navigation unit, and Lybid K-2RB digital radio (under license from Motorola) providing secure communications with a 70 km range.

[citation needed] In August 2019, Ukroboronprom announced the Lviv Armoured Plant (LBTZ) had also started modernizing T-64s to the 2017 standard.

It features "new up-to-date radio stations" and additional "navigation, internal and external communication systems which fully meets NATO standards."

[19] Sources differ on the initial production date of the tank that is set between 1963 and 1967, but it is established that the T-64 formally entered service with the Soviet army in 1967 and was publicly revealed in 1970.

Meanwhile, the T-72 was intended to supersede the T-55 and T-62 in equipping the bulk of the Soviet tank and mechanised forces, as well as for export partners and east-block satellite states.

In light of Soviet doctrine, the superior T-64s were kept ready and reserved for the most important mission: a potential outbreak of a war in Europe.

It appears that the tank remained secret to the West for some years between its entry into production in the early 1960s and the official acceptance in the Soviet Army in 1967.

A few T-64 tanks were tested in Afghanistan[41] during January 1980, but were quickly withdrawn without seeing combat because their engines did not perform well in the high altitude necessary for Afghan operations.

[40] After the dissolution of the Soviet Union in 1991, the new Russian Ground Forces decided to standardise the tank fleet with the T-72 and the T-80, and the T-64s were gradually put in reserve storage or scrapped.

[39] In June 1992, 18 former Soviet T-64BV tanks from the Odesa Military District's 59th Guards Motor Rifle Division were taken over by the Transnistrian Army, fighting in the Transnistria War.

[44][45] Donating surplus T-64s to the separatists was seen as cost-effective and deniable because the Russian military no longer had any use for the tanks and they could be passed off as individual examples captured from the Ukrainian Army.