Why do Russian tanks have cages on them?
This contraption atop the Russian tank is a ‘pergola’.
It is ‘useful’ for urban and air to ground rocket defense. However, the downside is that the structure literally points out with a glaring bullseye that the top is extremely weak in combat operations.
Specifically many of the lead tanks in formation have them to defeat the now famous Javelin missiles.
The Ukrainians reported the “Holy Javelins” cut through the pergolas like “Shit through a goose” and killed or incapacitated the crews.
Essentially, it is a version of a whipple shield meant to stop the damage to the hull by squash head ordnance.
It explodes further away from the surface!
Tank crews used to put track pieces or tree trunks on their tanks for the same reason, all modern tanks have this sort of protection against anti-tank fire
Often they use reactive armor or even electric armor which as the projectile hits the outer plate it shorts out what is effectively a welder and the projectile melts and splashes on the hull instead of penetrating,
It’s the ERA that is supposed to stop a two-stage ATGM. However, the Javelin has a top-down attack mode.
However, the two-stage Javelin warhead has a specific design to defeat ERA.
In Vietnam, they used chain-link fence material to detonate the B-40 rockets before they hit the actual armor. It must have worked because they kept doing it.
The Soviets, in Germany, would collect mattresses in piles, burn them, then mount the wire coils on their turrets.
Of course most tank minds know that the Germans need to reinforce their Panzers in WW2. Many WWII German tanks had spaced armor in the form of armored skirts. To make their thinner side armor more effective against anti-tank fire.
Its introduction was to counter Soviet anti-tank units using conventional kinetic penetrator type rounds (anti-tank rifles), not the bazooka, panzerfaust, and other HEAT weapons as commonly thought. See our piece: What was the Achilles Heel of the Panzer Tank?