Enemy Systems in Acceptable Losses are reflected in two variables that affect missions and appear in the nightly Intel Reports:
Enemy Defenses
Enemy Activity
There is also one hidden variable that simulates the fog of war:
Local Manpower Pool
Enemy Defenses
Only successful mission outcomes can reduce Enemy Defences, so hit them hard when you can. The enemy doesn't rebuild their fortifications during missions, they wait until dark.
During the Night Phase, Enemy Defenses may recover, with the chance of recovery modified by Weather and Enemy Activity.
Bad weather makes trench maintenance more difficult, just as it does for the player.
Low Enemy Activity reduces the chance of repairs, as the enemy is occupied elsewhere.
Enemy Activity
Enemy Activity is more dynamic.
It can decrease through mission outcomes and mission events. This represents enemy casualties and disruption.
It can increase through mission outcomes, mission events, and night events. This represents the enemy shifting forces along the frontline in response to your actions. Where activity rises, more soldiers are moved into the sector.
Enemy Activity can also increase by chance during the Night Phase. This represents reinforcements arriving. The reinforcement mechanic is influenced by two modifiers: Weather and Local Manpower Pool.
Bad weather slows enemy reinforcements, just as it does for the player.
Local Manpower Pool
The Local Manpower Pool represents how many reinforcements are available to that sector over the course of the campaign.
When a night reinforcement roll succeeds, the Manpower Pool decreases and Enemy Activity increases.
The Manpower Pool can also change independently of Enemy Activity. This simulates reinforcing neighboring sectors or wounded soldiers returning to duty. Since the player cannot see these numbers, the goal remains simple: reduce Enemy Activity whenever possible.
Bottom Line
Enemy systems are meant to feel reactive, not scripted. The front shifts. Pressure builds. Reinforcements arrive, or not. What you see in the Intel Report is only what HQ is able to show you.
If you would like to see more breakdowns of the systems behind Acceptable Losses, follow here or join the Discord.