Key point: The T-72 was a good tank and has been continuously upgraded. Today, Moscow intends to keep the T-72 in service in addition to newer tanks.

When the Soviet T-72  tank was first deployed, Richard Nixon was President, the F-4 Phantom was America's primary fighter, and the world's steel beasts had yet to discover a nemesis called the wire-guided anti-tank missile.

At least 25,000 T-72s have been built, making it the second-most prolific post-World War II tank, coming in behind only the ubiquitous T-54/T-55. That the T-72 is still in service today -- and still being used by about 45 countries, including Russia -- speaks to the longevity of this vehicle.

The T-72 began life as a cheaper alternative to the disastrous T-64, a sophisticated mid-1960s tank that proved to be over-complicated and unreliable. First deployed with the Soviet Army in 1973, the 41-ton T-72 featured a 125-millimeter smoothbore cannon. The cannon was fed by an autoloader instead of a human loader, just like the T-64, enabling the vehicle's crew to be reduced to three instead of the usual four in modern tanks. However, unlike the T-64, the T-72 didn't try to feed the crew's limbs into the gun.

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With a Rolled Homogenous Armor - a measure of armor toughness -- of about 410 to 500 millimeters for the cast-armor hull and turret, the original T-72 had decent armor protection for an early 1970s tank. However, it also carried ammunition in the crew compartment rather than a separate, protected space, which increased the risk of a catastrophic explosion when the vehicle was hit. So many damaged T-72s in Iraq blew their turrets off that U.S. troops called them “jack-in-the-boxes.”

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What's notable about the T-72 is how it has been upgraded over the years, as well as its numerous variants. The T-72A appeared in 1979, with thicker armor. "The thickened appearance of the turret frontal armor of the T-72A led to the unofficial U.S. Army nickname "Dolly Parton’ for this variant, after the buxom American country singer and actress," writes tank experts Steven Zaloga in his book "T-72 Main Battle Tank 1974-93".

Next came the T-72B in 1985, which incorporated features from the newer T-80. In particular, the T-72B had a laser rangefinder and thicker armor of as much as 560 RHA, with the turret beefed up with composite armor.

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It was the T-72BI version that really had a well-protected turret ("Super Dolly Parton" composite armor). The Soviets were particularly concerned with shaped-charge shells and rockets; The T-72BI's hull and turret had a remarkable 900 to 950 RHA against HEAT warheads.

The T-72B and BI also had the capability to fire missiles from their 125-millimeter cannon. The 9M119 Svir and 9M119M Refleks missiles -- NATO code name AT-11 Sniper -- are two-foot-long, laser-guided missiles with a range of more than 3 miles. The T-72B and later models were also equipped with explosive reactive armor, or ERA, to destroy incoming shells before they hit the vehicle.

The T-72B2, unveiled in 2006, has advanced Relickt ERA protection, the Shtora-1 jamming system to disrupt missile guidance links, and a more powerful, 1,000-horsepower engine.

The latest upgrades, displayed in 2010, is the T-72B3 and B3M. Intended as a cheaper upgrade than the T-72B2, the B3 program refurbishes old T-72Bs with a new engine, better fire control and a more powerful cannon.

Unfortunately for T-72 fans, there are numerous home-grown variants developed by non-Russian customers. Among others, Saddam Hussein's Iraq had "Lion of Babylon" T-72s, Yugoslavia had its M-84, India the Ajeya, South Africa the T-72 Tiger upgrade package and Syria the T-72 Adra.

There are several thousands T-72s in use around the world. Not surprisingly, the biggest user is still Russia, with about 2,500 in active service and another 8,000 in reserve. As of September 2016, about a thousand T-72s have been upgraded into B3 models, according  to a Russian defense site.

While Russia has 3,500 T-80s, that tank seems to be a dead end. While the T-14 Armata is an intriguing and sophisticated next-generation tank, it seems unlikely that it will be mass-produced enough to become the primary Russian main battle tank any time soon. Which means that for the foreseeable future, the T-72 will continue to be the backbone of Russia's armor fleet.

Michael Peck is a contributor to the National Interest and is a regular writer for many outlets like WarIsBoring. He can be found on Twitter and Facebook. This first appeared in 2017.

Image: Reuters