or rice mats to lure the Japanese into trying to board, since the boarding would appear safe. However, modern authors have found this to be unlikely since such an arrangement would have invited enemy fire arrows. Cannon The turtle ship was equipped with Cheonja "Heaven", Jija "Earth", Hyeonja "Black", and Hwangja "Yellow" type chongtong (Joseon cannons). There was also an arquebus known as Seungja (Victory). The Seungja ranged while the Hwangja was the lightest but with a range of . According to Hae-Ill Bak, one Japanese record of the Battle of Angolpo records the experience of two Japanese commanders on July 9, 1592, in their battle against turtle ships: "their (turtle ships') attack continued until about 6 o'clock in the afternoon by firing large fire-arrows through repeated alternate approaches, even as close as 18–30 feet. As a result, almost every part of our ships — the turret, the passages and the side shielding — were totally destroyed..." Tactical use 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). The turtle ship's main use of the plating was as an anti-boarding device, due to the top plating of the turtle ship and its protruded spikes. Grappling hooks could not gain direct hold on the plating, and jumping on top of the turtle ship often meant being impaled. The heavy timber plating deflected arrows and arquebus rounds. Later, the turtle ship was used for other purposes such as spearheading attacks or ambushing Japanese ships in tight areas such as in the Battle of Noryang. Despite popular depiction, the turtle ship was not an extremely slow ship. The turtle ship had oar propulsion as well as sails, and could turn on its axis like the panokseon. Admiral Yi constructed the turtle ship to be fast and agile for the purpose of ramming. Turtle Ships played a major role in the Korean victory over the Japanese navy in the Battle of