US/UK armor dominates battlefields due to advanced technology. When they engage other AFV classes, the result is a turkey shoot. The Soviet T-72 became a parade ground tank.

There has been a steady evolution of tank armor and weaponry. In World War I, tanks had thin armor shells designed to deflect bullets and shrapnel. Tanks were infantry support vehicles and were designed to attack infantry and provide protective cover for friendly infantry. Basically, they were rolling pill boxes.

The interwar period and World War II forced major changes to AFV design.

There were changes in fuel types. German tanks early in WWII used gasoline. If the fuel tank was hit, the tank exploded. The Soviets used Diesel for their tanks, like the T-34. If struck, it burned slowly so it was safer for the crew. The tradeoff was that diesal emitted think black fumes that gave away the positions of Soviet tanks.

Armor and weapons grew more complex.

High explosive (HE) ammunition, used by early tanks and artillery, is not cost-effective against armor. HE shells explode spherically, so most of the blast is directed away from the armor. It scales poorly, so doubling the high explosives does not double the armor penetration. As tanks used larger HE rounds, steel armor simply increased in thickness to counter it.

By World War II and well afterwards, tanks used High Explosive Anti-Tank rounds (HEAT). HEAT rounds use explosively shaped charge that creates a jet of melted copper to penetrate armor.

Instead of exploding spherically like HE shells, a HEAT shell funnels its power in a cone-shape direction directly into the armor. Thicker armor provides less protection against this class of armor piercing shell.

HEAT rounds were fired through rifled tank gun. The rifling gave it high accuracy even though it was less effective. Tanks needed to completely stop, aim and fire to accurately hit anything.

During WWII, tanks developed sloped armor.
Sloped armor greatly increased armor strength. It could cause ricochets. It deflected explosive blasts away from the center of the tank so explosions were more likely to graze the surface of the armor. By placing armor on an angle, it enhanced armor thickness without actually increasing the thickness of the plate. Due to the angles, a thinner plate of sloped armor provides the same thickness as a thicker flat plate. Sloped armor enhances protection and reduces weight and profile.

The T-34 was one of the best designed WWII medium tanks in part because of it’s sloped armor, diesel engines, and large cannon.

Tank designs relied on sloped armor and HEAT until the late 60s and 70s.

Two developments rendered Soviet Tanks obsolete and allowed US/UK tanks to dominate the field.

Chobham Armor is a honeycomb of steel and ceramic armor. It actually reverts to flat armor blocks, which gives the M1 Abrams its boxy shape. The honeycomb disperses the HEAT jet in various directions. HEAT rounds cannot penetrate through the armor.

Sabot rounds replaced HEAT rounds for Western Tanks. Sabots are a kenetic energy projectile. The M1 fires a sabot from it’s 120mm smoothbore gun – the sabot is discarded soon after firing. The actual round is about 40mm in size. It’s like the finger of God. It moves at such a high-velocity, that it can penetrate all known armors, including Chobham.

Sabots are very inaccurate. Rifled cannons slow their velocity to increase accurace, so tank designers prefer less accurate smoothbores. The United States created a computerized targeting system that greatly improves accuracy. Amazingly, US tanks can fire while moving and hit with stunning accuracy.

US/UK tanks are further aided by night vision and thermal vision technology. They can see better and hit more accurately than any other tanks in the world.

Soviet tanks, like the contemporary T-72, continued to use sloped and curved armor. The T-72 uses a smoothbore sabot firing gun, but it cannot hit anything. Soviet engines were also inferior by this point, so the T-72 and other models were prone to breakdowns.

By the 1970s to 1990s, the Soviets could only produce Parade-ground Tanks.

This generally matched the relative economic capabilities of the United States and the Soviet Union. The US had more advanced computer and industrial technology while the Soviets could only churn out low-quality junk.