In 1957, the D-56T gun was replaced with the D-56TM - with double-baffle muzzle brake and fume extractor - and the hull was raised by 13 cm; additionally the tank was equipped with new vision and communications devices.

The driver sits in the center of the front of the hull and has a one piece hatch that opens to the right, with three vision blocks and periscopes located beneath the main gun at the top of the sloping glacis plate.

Its main armament consists of a 76.2 mm D-56T series rifled tank gun, which has an effective range of approximately 1,500 meters and a rate of fire of six to eight rounds per minute.

One of the greatest disadvantages of the gun used on the PT-76 Model 1 was that it had no stabilization system and therefore couldn't be effectively fired while the vehicle was on the move.

[1][3][6][8][9] The torsion bar suspension consists of six evenly spaced large rubber-tired road wheels with the drive sprocket at the rear and the idler at the front.

[1][6][7][8][10][11][12] The PT-76 is amphibious, it has a flat, boat-shaped hull which is hermetical and ensures minimal resistance when the tank is afloat.

When not in use the trim vane is stowed in the front of the bow under the barrel of the main gun and serves as additional armor.

However, its amphibious design makes it disproportionally large for a vehicle of its weight and allows less armor protection than other light tanks.

[1][6][7][11] The PT-76 is equipped with a tank communication device, a gyro compass, a 10-RT-26E radio with an antenna that extends itself when needed.

It lagged behind other Soviet armoured fighting vehicles because only the driver had a night vision device and also because it has no fire or NBC (nuclear, biological, chemical) protection systems, which significantly reduced its effectiveness.

Over 25 countries employed the vehicle, including Afghanistan, Albania, Angola, China, Congo, Cuba, Egypt, Finland, Guinea, Hungary, India, Indonesia, Iraq, Laos, Madagascar, Mozambique, North Korea, Pakistan, Poland, North Vietnam, and Yugoslavia.

Although it has been replaced in front line service by the BMP-1, it may still be found in the reconnaissance companies and battalions of some motorized rifle and tank regiments and divisions, as well as in naval infantry units.

Aside from its reconnaissance role, it is also used for crossing water obstacles in the first wave of an attack and for artillery support during the establishment of a beachhead.

Also, both vehicles have stronger front armor and superior mobility features and the BMP-1 can carry up to 8 fully equipped soldiers inside.

[18] Soviet PT-76s along with T-54s, T-55s, and Chinese Type 59s tanks formed the bulk of the People's Army of Vietnam (PAVN) armored forces.

The first successful action of PAVN armor in Vietnam was against the Lang Vei Special Forces camp on 6/7 February 1968[19] (they had already been used in the preceding Battle of Ban Houei Sane, which was just across the border in Laos however).

Thirteen PT-76s, of the PAVN 202nd Armored Regiment spearheaded an assault against approximately 24 Green Berets, 500 South Vietnamese irregulars and 350 Laotian Royal soldiers.

[19] The Lang Vei camp was overrun, with the PT-76s using their turret-mounted spotlight-equipped heavy machine guns to shoot down any irregulars who panicked and ran out of the underground bunkers.

The first tank-to-tank engagement occurred in mid-1968 when a US reconnaissance airplane observed a PT-76 being washed by its crew in the Bến Hải River in the DMZ (17th Parallel).

Shortly afterwards, some returning F-4 Phantom jet fighter bombers, with ordnance to expend, observed the PT-76 and bombed the remainder of the vehicle.

[21] On March 3, 1969, the Special Forces' Ben Het Camp was attacked by the PAVN 202nd Armored Regiment.

Flares had been sent up, thus exposing adversary tanks, but sighting in on muzzle flashes, one PT-76 scored a direct hit on the turret of a M48, killing two crewmen and wounding two more.

[23] On April 24, 1972, the US special experimental 1st Combat Aerial TOW Team arrived in South Vietnam.

From May 2, the team made daily flights in search of enemy armor, with the missiles mounted in the XM26 three-tube launcher.

TOW aircraft were brought in at first light and found PAVN tanks moving almost at will through portions of the city.

Conventional air strikes would have been risky for friendly forces, and the TOW proved to be ideal for picking off enemy tanks.

The tactics of the Indian Army enabled the PT-76 to play a vital role in the Eastern theater of the 1971 war where the PT-76s proved superior to the obsolete Pakistani M24 Chaffee light tanks despite being outnumbered.

A good example of such an engagement was the Battle of Garibpur, where an Indian Army Infantry Battalion with only 14 PT-76s was able to maul a much larger brigade-strength unit of Pakistani armor and inflict heavy casualties.

During the Yom Kippur War in 1973 PT-76s were used during the crossing of the Great Bitter Lake by the Egyptian 130th Marines Brigade.

][30] The People's Armed Forces of Liberation of Angola (FAPLA) deployed PT-76s during the Angolan Civil War, as did Cuba during its lengthy military intervention in that country.