This was the first tank designed for nuclear war
After America dropped the atomic bombs at Hiroshima and Nagasaki, it became clear that warfare had changed. America stopped building some conventional weapons of war, including tanks, relying on the new weapons to guarantee peace. Meanwhile, the Soviet Union was working on two new, important weapons of war: their own atomic bombs and tanks that can protect a crew through the blast.
The T-54 had a massive gun that surprised its contemporaries in the 1950s, but it predicted the rise of the modern main battle tank.
(ShinePhantom, CC BY-SA 3.0)
The Soviet Union didn't have the resources to compete with America tank for tank and bomb for bomb worldwide, but they did hope to control as much of Eurasia as possible, and they knew this would result in a clash along the borders of the Warsaw Pact and Western Europe.
The Soviet military leadership wanted to know that, even if a tactical nuclear exchange went down, they would be able to fight through the aftermath. That meant that their tank crews needed to be lethal, protected from anti-tank weapons, but also isolated from nuclear fallout.
And so they turned to their T-54B tank and started prepping it to survive the blast of the strongest weapons known to man.
Polish T-54 tanks.
The T-54B was already an impressive tank, first rolling off the line in 1949. It was simple to operate, relatively cheap for a main battle tank, and well-balanced. The Soviets and the partnered nations that would go on to buy export version of the tank saw it as a successor to the T-34, the most produced tank of World War II.
But the tank was more accurately a descendant of the T-44, a tank with a gun so big that firing it would wear down the transmission. The increased firepower in the T-44 and, later, the T-54, would be necessary in tank-on-tank combat on any Cold War battlefield.
But the early production T-54s still had plenty of faults, and tank designers improved the platform throughout the 1950s. The T-54A and T-54B introduced upgrades like wading snorkels, fume extractors, and an upgraded gun called the D-10TG. The T-55 was designed with all the knowledge and upgrades from the T-54's development. The T-55 would be lethal right off the starting block. But being a lethal medium tank isn't enough to survive nuclear war.
A Slovenian M-55, a highly modified T-55 medium tank.
(MORS, CC BY 3.0)
Believe it or not, the primary systems of a tank in the 1950s were about as survivable as they could be from the bomb. Obviously, no tank could survive at ground zero of a nuclear bomb, but it would be possible for a tank to survive the blast near the borders of the area affected. After all, the armor is designed to survive a direct hit from a fast-flying, armor penetrating round at any given point. An atomic bomb's blast is more powerful, but it's spread out over the entire hull and turret.
But there was, of course, another major danger while fighting a nuclear-armed rival. After the fireball and after the blast, the irradiated dust and debris would fall back down to earth. For crews to survive, they would need safe air and living space.
And so the designers figured out how to overpressure the tank, creating higher pressure within the tank so that all of the little leaks in the armor were pushing air out instead of allowing it in. And the crew compartment was covered in an anti-radiation lining that would reduce radiation traveling through the hull. Finally, a filtration system cleared incoming air of debris and then pumped it into the crew cabin, allowing the crew to breathe and making the overpressure system work.
Again, none of this would make the crew immune from the effects of a bomb. The blast wave could still crush the hull and burst blood vessels in the brains of the crew. The heat wave could still ignite fuel and fry the people inside. Worst of all, plenty of radiation could get through and doom the combatants to deaths of cancer.
But the crew would likely survive to keep fighting, and had some chance of a decent life after the war if they made it. For a few years, at least.
The T-54 and T-55 went on to become the most-produced tanks in world history, but luckily the T-55 adaptations were never actually tested in combat. It and the British Centurion would undergo testing for nuclear blasts. They survived, but you really didn't want to be inside when the blast hit.
The Object 279 heavy tank was designed for nuclear warfare, but it never went into production due to its high weight.
(Alf van Beem, public domain)
Oddly enough, the T-55 was the first production tank to be designed for nuclear warfare, it wasn't the only Soviet design that flirted with surviving a nuclear war. Russian weapon designers also came up with the Object 279, a heavy tank with four sets of treads that was supposed to enter production even before the T-55.
But it wasn't to be. Soviet leader Nikita Khrushchev thought it was time to relegate heavy tanks to the dustbin of history, and he won out. Object 279 and most other heavy tank designs were cast out, leaving the path open for the lighter T-55 medium tank.