Circumvallation :: Circumvallation (n.) The act of surrounding with a wall or rampart.
Circumvallation :: Circumvallation (n.) A line of field works made around a besieged place and the besieging army, to protect the camp of the besiegers against the attack of an enemy from without..
Contravallation :: Contravallation (n.) A trench guarded with a parapet, constructed by besiegers, to secure themselves and check sallies of the besieged..