The defences around Leningrad are quite formidable, my only chance of taking the city quickly with limited losses is by cutting those forces off, which my Panzer attack will hopefully do. Cut-off units in WitE suffer some serious penalties to morale and combat power, so even large, well dug-in armies will succumb to attack in a short time.
There are fewer examples of successful breakouts of encirclements in military history than examples where they failed. Especially mechanized and armored forces will quickly succumb out of necessity if cut off from fuel supply. Ammunition consumption, though moderate by today's standards, was unprecedented in WW2, and certainly put another serious strain on the supply chain. In some respect modern armies are more vulnerable to encirclements than they used to be at times where you relied on pointy sticks and sharp blades primarily. But as long soon as your side runs out of fuel and ammo and the other side still has it, resistance (on a large scale) is futile.
Willpower and heroism is not enough to break a tank's armor, or to protect from its MG bullets.
