I am referring to for example, If WWII tanks are able to destroy a modern tank. Obviously modern tanks have much better armor and overall protection than WWII tanks, but I very much doubt it is 100% immune to everything a WWII tank throw at them. Back in WWII, Tiger and Tiger II tank, and Panther from the front are largely immune to the gunfire of allied tanks such as Sherman and T-34 at normal engagement range. But often time the allied tanks came with overwhelming numbers, which enable them to get close enough for a kill shot either from the side, or the rear, or sometimes even a frontal shot at close enough range can still penetrate what they normally couldn't. Obviously modern day tanks' 120mm and 125mm gun combined with modern optical, modern firing control system will most likely one shot WWII tanks at 2~3km range. But some WWII tanks are also known for be able to kill enemy tanks at 2~3km range, such as the famous 88mm on Tiger 1. There is also 128mm on JagdTiger (a tank destroyer). I remember hearing "A RPG-7 could knock out a M1A2 tank if hit the right spot"...and RPG-7 isn't even all that powerful. Do you think these guns might still effective in knocking out modern tanks like Challenger, Leopard 2, M1A2, etc. under certain distance or from certain direction?