The most-produced tank in military history. Perhaps one of the most battle-tested tanks ever. Nearly 70 years of service and no end in sight.

Each of these describes the T-54/55 series of tanks, designed by the Soviet Union in the aftermath of the Second World War, incorporating incremental changes that keep the series still relevant on some of the lower-intensity battlefields of today.

Firepower

In the years following the Second World War, Soviet engineers began experimenting with the venerable T-34 tank design and the newer, but only modestly produced T-44 tank. Increased firepower was needed, and could be realized by a longer, larger caliber gun. But the small internal size of the T-34 and T-44 made this difficult from an engineering standpoint — the turret was too cramped, and it would be difficult to adjust wartime production lines that had been optimized for churning out T-34s.

Realizing the obsolescence of the World War II era T-34 gun — a puny 76.2 millimeters — designers settled on a 100 millimeter gun, necessitating a somewhat larger turret, and expanded hull to accommodate the increase in turret size. The somewhat larger T-44 would not suffice, something new was required.

Protection

In comparison to the T-34, the T-54/55 had enormously think frontal armor— a whopping 100-120 millimeters, depending on the variant. Once the Soviet Union entered the nuclear age, vulnerabilities to nuclear explosions became apparent, and engineers brainstormed ways in which to keeps tanks and tank crews in the fight, even if a war went nuclear.

T-54s were used to test survivability against nuclear weapons. While the tanks themselves could survive indirect nuclear strikes from a distance, the crew would quickly succumb to the radiation aftereffects of a nuclear explosion. T-54s were outfitted with emergency NCB (nuclear, chemical, biological) protection systems.

Soviet doctrine favored implementing incremental upgrades during scheduled maintenance overhauls, rather than broader, sweeping changes being done less often.

The distinction between the T-54/55 families is, therefore, minor — both tanks are outwardly quite similar.

Mobility

With a total weight in the modest mid- to high 30-ton range, the T-54/55 series had a decent power-to-weight ratio. In keeping with lessons learned from World War II designs, and from the T-34 in particular, the series kept the wide tank treads that define the T-34 design. A low-pressure ground footprint allowed for good mobility even in soft, muddy terrain, typical in Russia during the spring thaws.

In comparison to today’s Main Battle Tank behemoths, like the M1 Abrams, the T-54/55 series benefits from simpler logistics. It’s modest weight easily allows quick rail transportation.

This remains a high priority for Russia, as its long borders and almost absurdly long distances are more easily overcome by rail transport, and is reflected today in its newest tank, the T-14 Armata, which is almost a featherweight in comparison to its American and NATO counterparts.

Today

The T-54/55 continues to serve in active duty or in the reserve inventories of many countries around the world, especially among state and non-state actors that do not have the resources to buy newer, more technologically advanced equipment. Many African, Middle Eastern, and Asian countries count heavily modified and modernized versions of the T-54/55 series on active or reserve duties.

Several private companies offer armor and firepower upgrade kits, including longer, higher velocity guns, and explosive reactive armor (ERA) to give the T-54/55 series a fighting chance against adversaries with more modern anti-tank weapons, or against newer, more advanced tanks themselves, keeping the T-54/55 series relevant in the 21st century.

Caleb Larson is a Defense Writer with The National Interest. He holds a Master of Public Policy and covers US and Russian security, European defense issues, and German politics and culture.