Only one unit at a time may occupy an arsenal, fortress, mountain pass, or other square.

Fortresses are not allied with a faction and can be occupied by any unit from either side. Fortresses do not propagate communication and cannot be destroyed.

An arsenal is destroyed if it is occupied by the enemy. Only empty arsenals can be occupied. The destruction of an enemy's arsenal counts as an attack, and no other attack may be deployed that turn. Note: Relay units have no offensive power and thus cannot destroy an arsenal.

Cavalry can not charge against a fortress or mountain pass; any cavalry currently occupying a fortress can not participate in a charge (although charging while in a pass is allowed).