Line of communication
Each Army has certain hierarchy. All Our Trenches will bring it to the level that it is crucial to preserve contact with all units and their officers.
Losing contact means that Commander i.e. player also losing ability to give orders to the unit until the time that contact is restored. This could be disastrous in the battle.
Fog of war
AoT brings advanced mode of fog of war, since units share own field of view with other units and commander only if communications are good and not disturbed or cut.
Lines of supplies
Units are consumers of different types of supplies and in different quantities. It is very important to provide troops enough material and ammunition, so they can achieve goals as rapid fire or crucial defense.
Troops that don’t have enough supplies will tend to lose moral, fighting abilities and will be easier targets for the enemy.