One or more allied units in the same zone as an unoccupied fortification can occupy it by spending an action during the Action phase. A unit can retire from a fortification without spending an act. Occupying a fortification gives the occupying units the fortification's Defense bonus. Siege units, and units with chariots, howdahs, or mounts cannot occupy a fortification; however, those units can temporarily unequip those resources, losing their benefits, but then be able to occupy the fortification. Unequipping a resource requires no action, but equipping it takes one act.
Enemy units cannot target units occupying a fortification with melee attacks, and vice versa. However, units can use ladder and siege tower siege units to use melee attacks against occupying units (see Siege Engines).
Fortifications are large enough to be an obstacle, allowing units to enter its zone, but not advance further to another other zone except for the one the units came from. Units with some special abilities can ignore a fortification as an obstacle to moving through its zone, such as Flight, (see Special Abilities).
Entry Points
In general, all fortifications have at least one entry point. A unit occupying a fortification can open its entry point, allowing units to pass through to other zones as normal. Upon constructing a fortification, you can decide how many entry points does it have, which cardinal direction each one is facing, and which lateral zone of the cardinal direction are they located in. You may decide to have no entry points at all, using more exotic means to pass through a zone with the fortification (such as flight, mass teleportation, or opening a portal to the other side). Removing or adding an entry point to a finished fortification costs 1 BP and takes 16 hours of activity.
Attacking and Damaging Fortifications
Units can use melee and range attacks to destroy a fortification. Fortifications have a DV equal to 15 + their Defense bonus. They reduce damage received by an amount equal to their DV (to a minimum of 0), except for damage from siege units. They have an hp value equal to 10 times their BP value. Units using melee attacks against a fortification become engaged, and are subject to flanking from enemy units. However, they do not require a Morale check to disengage from the fortification; the normal disengage rules applies against other units the unit is also engaged with.
When a fortification's hp falls to half of its total or lower, the fortification becomes breached. A breached fortification allows units to pass through the zone it occupies, but at the cost of two Advance acts due to the unit having to squeeze through the breach and overcome debris. The breached fortification still provides its Defense bonus to its occupied units, but those units can now be attacked with melee attacks.
When their hp is reduced to zero, they are destroyed. A destroyed fortification no longer provides any Defense bonus to units, cannot be occupied by units, and are no longer an obstacle on the battlefield. It still takes two Advance acts to move through a zone with a destroyed fortification as units need to navigate around significant debris.
Repairing Fortifications
Once a fortification becomes breached, the occupying army can pay BP equal to the fortification's Defense bonus to repair it. Repairing a fortification requires 8 hours of activity for a platoon. The repair time is halved for every unit size category larger, to a minimum of 1 hour. A destroyed fortification can be repaired in the same way, but the occupying army must pay the BP cost twice, once from destroyed to breached, and again from breached to fully repaired.
Area
Each type of fortification occupies a number of zones based on its size and purpose, as described in Table: Fortifications under "Area Occupation". However, a fortifcation can occupy fewer zones if the commander of the side that initially owns it so chooses. When setting up on the battlefield, the commander can decide to have a fortification occupy fewer zones. The fortification's size does not change; rather, it is the commander's choice to redesignate and expand battlefield zones to match his strategy.
Table: Fortifications
| Building | Defense Bonus | hp | Area Occupation |
|---|---|---|---|
| Aerie | +3 | 180 | 1 zone. |
| Barracks | +4 | 60 | Up to 2 by 2 zones. |
| Castle | +16 | 540 | Up to 4 by 3 zones. |
| City Stone Wall | +8 | 80 | Up to 1 by 3 zones. |
| City Wooden Wall | +2 | 20 | Up to 1 by 3 zones. |
| Fort | +16 | 240 | Up to 3 by 3 zones. |
| Garrison | +8 | 120 | Up to 2 by 3 zones. |
| Moat | +1 | 20 | Up to 1 by 3 zones. |
| Watchtower | +2 | 60 | 1 zone. |