not too many battles, given that we have the computing abilities of not only the cpu, but the gpu as well.
the question is not just the amount of armor, but how this amount is used. here is a look, if you have 50 hitpoint, armor that reduces damage by 5, and hit you ten times with a force of 10, then (10-5)* 10=50 - i.e. you are always dead. as we can see now the game works like this. and now the same situation, but the armor does not reduce damage, but only in 50% of cases completely blocks the damage(as if the enemy missed). and there are already possible options: if you are lucky, you will not even get scratched in ten strokes, and if your luck is bad, you will die twice. yes, on large numbers, this algorithm will approach the results of the first, but only in total, and for each fighter separately, it will still give random results. we do not just sum up the health, defense and attack of each army, then do something with it, but we will count random pairs of fighters from each army - that is, we will practically simulate a real fight(yes! how many times have you been killed with a pitchfork by a peasant? that is because in the real world people screw up. so there will be nothing wrong if a horse archer is defeated by an infantryman in such a simulation).
but this approach is suitable not only for simulation, but also for real combat- not every arrow that physically hits the body should cause any damage.