I agree … especially today, even with all our high tech … sometimes
happens. Having at times served in both a Bn TOC/ALOC and later a Bde TOC/ALOC, '80-'90 … But again, today there is more higher tech on the battlefield.
Note back then we only had C3[Command, Control, Commo] but today it is C4I – Command, Control, Communications, Computers, & Intelligence (US DoD). 
For fog of war, you could and random events cards or charts.
We also use random missions for both Attacker & Defender. Each draw a numbered chit from a separate chit cup. This done secretly.
Your opponent does not know what your mission is.
The only thing each player knows is if they are attack or defending. Rolling off 1D6 before the game. High roller chooses.
Once each player draws its secret mission chit. The number relates to a mission list, with victory conditions, special deployment rules, if the basic force level stays the same, goes up or goes down, etc.
Before the game the players decide how points will be used, e.g. 1000 pts is a smaller battle where 6000 is a bigger game. We use 1000-6000 pts levels.
E.g. your Mission may add 500 pts or lose 500 pts. From your basic force level. So, the game may be a 3000 pt. But you may lose 500pts so now you only 2500 pts to use for your forces. Or just the opposite, now you have 3500 pts. Again, all done secretly.
The Mission may state you only get 1/2 of your points at the beginning of the game. Then on turn 3 you get the rest of your forces. Or you have to roll a 1D6 at the beginning of the game to see if those forces come on turn 1 or 2-6.
E.g. The forces may come in on your side of the lines. Or on the East side or West side of the border within so many 36cms/inches from your own lines.
This may take some time to come up with the 7-9 missions for the Attacker and defender, but it is worth the work IMO.
The Attacker may have to get 1/2 of his force off the enemy's side of the board.
Just some suggestions … that may or may not work for you. Use your imagination as well as actual military history …