Yi resurrected the turtle ship as a close-assault vessel, intended to ram enemy ships and sink them, similar to their use in past centuries. Despite smaller numbers, disabling or sinking enemy's lead command ship could severely damage command structure and morale of the enemy fleet. After ramming, the turtle ship would unleash a broadside volley of cannonballs. Because of this tactic, the Japanese called the turtle ships because they would blast and ram into enemy ships. This kind of attack was used during the Battle of Dangpo and Battle of Sacheon (1592).