Overrun is an effect of overpowering the enemy in Civilization Revolution. If a unit's attack is much higher than the defense of a unit it is attacking, the attacker will overrun the defender and automatically win the battle.

The attack/defense ratio required for an attacker to overrun a defender is normally 7:1 against other civilizations' units and 14:1 against Barbarians (when attacking with a single unit). The starting bonus of the Zulu, however, reduces this ratio to 3:1 against other civilizations and 6:1 against Barbarians.