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His Arsenal

1. Battleships

1.1 Panokseon ship

Panokseon ship was main warship of Joseon fleet. Its name means literally wood warship having panok, loft on it. Commander boarded on this loft while Oarsmen and soldiers boarded in gun deck. Koreans added tall wood plates in both side of a ship above upper deck because Japanese main naval tactic was boarding tactic which navy board enemy’s ship and fight on their ship’s deck by sword.

It was also designed to sail in southeastern coast of Korea which has wide mudflats and many large and small islands. Hence this ship had flat keel. Its structure was sturdy than Japanese warships, because Koreans used wooden nail to fix planks when they build this ship and it was made of sturdy pine wood plates. Therefore it was able to absorb reaction which occurred after the gun was pushed backward by the force of the blow. On the contrary, Japanese ships couldn’t absorb reaction, because they fixed planks with iron nails and their ships were made of Japanese cedar. This wood was less solidity than pine tree. Hence it couldn’t carry guns on it.

Admiral Yi’s fleet was composed of this ship in most battle. It followed Geobukseon and bombard Japanese fleet. He built 24 ships before the Imjin war broke out and built more ships during war period. His famous formation, Hakikjin, was able to position due to this ship. Furthermore, he could defeat Japanese fleet far away by guns. It was one of reasons why he could gain continue victories till the Imjin war ended.

1.2 Geobukseon ship

It is also known as turtle ship. Geobukseon means literally turtle shaped warship in Korean. It was similar as floating turtle. According to Lee Chungmugong Jeonseo, Biographies of Yi Sun-sin, the Geobukseon ship which was used during the imjin war period was designed by Admiral Yi Sun-sin and built by his subordinate naval officer, Na Dae-yong. According to T'aejongsillok, Annals of King T'aejong, Joseon scientists already invented turtle warship and had launch it in Hangang river. This test launch occurred during T'aejong's reign, 1401~1418. But, modern Korean historians inferred that this ship was quite different as the Geobukseon ship which used by Admiral Yi's fleet.

Sailors inside of this ship could see the enemy, but enemy couldn’t see its inside. It made Japanese to confuse where they shall attack. It was double-deck ship and propelled by sails and oars. There were cabin and warehouse in the first deck. It carried four series of guns in the second deck and Soldiers and oarsmen boarded on it. Its figurehead was dragon’s head to frustrate Japanese because they scared dragon the most. There was a wooden crest which rammed enemy ships below the dragon’s head.

It could discharge fires from the four directions. Inside of the Dragon’s head, it carried Hyeonjachontong and fired when it rushed to Japanese battle line. It carried 6 Chenjachongtong or Jijachongtong in broadside and approximately 1 gun in stern.

Admiral Yi built 3 Geobukseon ship before the Imjin war broke out. It was employed in the Battle of Sacheonpo for the first time. In battle, it led whole fleet and attacked Japanese ships first. After it dispersed Japanese battle line, remaining warships followed it. The main target of this ship was Adakebune, flagship which Japanese commander boarded.

2. Firearms

Firearms were first introduced to Goryeo, medieval state of Korea in 1104, but these weapons were extensively developed after Choi mu-seon developed method to produce gunpowder and established special government agency, Hwatongdogam in 1377. Joseon people also had developed various guns, muskets and shots. This development became one of reasons why Joseon fleet could defeat Japanese.

2.1 Guns
Four series of guns, Cheonja, Jija, Hyeonja and Hwangja were used during Imjin war period. Ancient Koreans gave different names for this four series of guns to separate their capability according to maximum range, number of balls and length. These guns mounted on Geobukseon ship and Panokseon ship. According to Nanjungilgi, war diary of Admiral Yi, he inspected naval bases when they test fire the guns in February 1592. He also drove his fleet and tested these guns of Geobukseon in the middle of south sea.

Guns comparison
	Cheonjachongtong	Jijachongtong	Hyeonjachongtong	Hwangjachongtong
Range	1,125m	1,000m	1,000m or 1,875m	1,378m
Calibre	118~130mm	105mm	60~75mm	40mm
Length	130~136cm	89~89.5cm	79~83.8cm	50.4cm

2.1.1 Cheonjachongtong : Cheon literally means sky in Korean. It was the largest gun and fired mostly Daejanggunjeon, cannon arrow to make a hole in the body of Japanese warships. It also could fire cannon ball and 400 Joranhwan, kind of shrapnel.

2.1.2. Jijachongtong : Ji literally means earth in Korean. It was the second largest gun and fired mostly Janggunjeon and 200 Joranhwan.

2.1.3. Hyeonjachongtong : Hyeon literally means black in Korean. It was the third largest gun and fired mostly Chadaejeon and 100 Joranhwan.

2.1.4. Hwangjachongtong : Hwang literally means yellow in Korean. It is the smallest gun and fired mostly Piryeongchajungjeon and 40 Joranhwan. The actual gun which was produced by gun artisan, Bu Gwi was designated Treasure Number 886, and preserved in the National Museum of Korea.

2.3. Musket
2.3.1 Jeongcheolchongtong : According to Nanjungilgi, , it was invented by the officer, Jeong Sa-jun under the admiral Yi. He compared Joseon’s matchlock, sungjachong with Japanese matchlock and invented it. It was made of refined iron.