The perfect assault will be broken up by that antitank gun you didn't see. You might have expected the enemy to have no tanks, only to find a large contingency of them thundering down on your line. A key leader will die by sniper fire at the most inopportune moment. There are no hexes, nor are there turns. It's all played in real time, with each shell computed individually, and morale playing a key role.
War is pure chaos, and too many games reduce it to black and white numbers.
The Close Combat series is sweet entropy and what every wargame should be. First on the list is the way artillery is handled. Off-board artillery finally makes an appearance, but it's limited to one type for either side, and the player has no control over it. Being able to buy salvos of various types before a scenario would have been great. Next, you can forget about a Henschel Hs 129 swooping down to devastate Russian armor with its 30mm MK 101 gun.