Yi Soon – Sin (or Yi Sun-Sin) A brief insight into the Man and the Turtle Boat

(Editor’s note: this essay formed part of Rosemary’s requirements for grading to 3rd Dan in June 2019)

Who was he?

Born 28 April 1545 – Died in battle 16 December 1598

We first hear the name Yi Soon–Sin in the pattern meaning of Choong – Moo

Choong-Moo was the name given to the great Admiral Yi Soon-Sin of the Lee Dynasty. He is reputed to have invented the first armored battleship (Kobukson) in 1592, which is said to be the precursor to the present day submarine. The reason this pattern ends in a left handed attack is to symbolize his regrettable death, having no chance to show his unrestrained potentiality checked by the forced reservation of his loyalty to the King. International Taekwon Do 1st Gup pattern

He was one of the great Korean Naval Commanders and helped redesign the Turtle Boat.

He was a great strategist and had many victories. He has been likened to Admiral Horatio Nelson for his undefeated record against seemingly insurmountable odds. 

Interestingly, he had no formal naval training.

Early Life

Yi, Soon-Sin was born in Geoncheon-dong, Hanseong which is now known as Seoul on the 28th April 1545.

His family was part of the Korean Deoksu Yi clan. His grandfather Yi Baeg-nok retired from politics when the neo confusian reformer Jo Gwang-jo was executed in the Third Literati Purge in 1519. His father who was also disillusioned with the politics of the time did not enter government service. This was expected of him as he was from a noble family. This showed a lot of integrity and fortitude to live by his principles and not the expectation of society.

Before the age of 28 when he first trailed for the Military Academy Yi Soon-Sin studied the liberal arts.

At this time in Korea: The King was not politically strong and did not have a firm hold over the court. There was a lot of infighting and vying for positions of power. Because of this there were often devious plots schemed to over throw rivals and put ones self in a stronger position.

The Korean people lived with very little, everything was done by hand and life was very hard. When the country was at war this took its toll on the poor the most. There was never enough food and the men went away to fight for long periods of time.

In 1572 Yi Soon-Sin at the age of 28 starts the military examination. His archery skills were impressive but he broke his leg during the cavalry examination. He had to wait 4 years for the next entry examination so was retested and passed in 1576.

He was then posted to the Bukbyeone (Northern Frontier Army). He was the oldest junior officer there at the age of 32.

He experienced battles defending the border settlements from the Jurchen and quickly became known for his strategic skills and leadership.

When Yi’s father died he spent 3 years out of the army. This was in accordance with the Confucian ideals of the time; he resigned his post to fulfil his filial duties as a mourner.

When he returned he again lead many successful campaigns against the Jurchen.

However, jealousy and spitefulness caught up with him. Many of his superiors felt threatened by his leadership skills, the loyalty his men were showing and the recognition he was receiving. It is said the King even felt threatened by him. There was a plot orchestrated and he was falsely accused of desertion during battle. He was striped of rank, imprisoned and tortured.

He was later pardoned and was allowed to reenlist as a soldier, taking up the  lowest rank possible. He did this happily and I believe in this action he showed the Taekwon do tenets of integrity, perseverance, self-control and indomitable spirit.

His skills were again recognised and he was later appointed to command a military training centre, after this he was transferred to a small county to be its military magistrate.

His break into the Navy came when he was posted Commander of the Left Jeolla Province Naval District in 1591.

This was a pivotal appointment for Korea. Once he was in charge of the Navy he took stock, looked at what assets they had in terms of ships and armaments. He looked at supply lines for food, and sources of food, and make changes as needed.

On of his projects was the modification of the turtle boat.

Turtle Boats

The Turtle boat was first designed under the reign of King Taejong.

Yi Soon-Sin decided to redesign the Turtle boat and rework the vessels armaments. It is believed there were no more than 12 turtle boats designed and no more than 5 went into battle at one time. The Turtle boat was quite small being approximately 30 metres in length. The redesigned Turtle boats were first used in the Battle of Sacheon (1592). Yi Soon-Sin used these boats to spear head the attack.

Yi designed several different styles of cannons. Part of the redesigning of the Turtle Boat was to flatten out the bottom slightly; this gave more stability when a cannon was fired.

The cannon balls could travel an astonishing 1200 metres, this compared to the Arquebus (early rifle), which had a range of 200 metres. Archery arrows were also used at the time.

The boats were redesigned with the thought of fighting the Japanese. The Japanese Navy used bigger boats which they would ram into an enemy boat, they would then board and fight with hand to hand combat. This was a very successful method of warfare for them.

The ships figurehead was a dragon (Although some sources say a turtles head). A dragon in Asian culture is very formidable.

Sulphur and saltpetre were burned to produce dense smoke, this came out of the dragoon’s mouth. Psychologically it was terrifying for the enemy to see this coming.

From the dragons mouth flames could also come out from a flamethrower (also invented by Yi Soon-Sin), this would set the Japanese ships alight.

Just below the dragons head was a large wooden crest in the shape of a face, this was used to ram enemy ships.

Cannons – 11 cannons down each side, two in the bow and two in the stern. There were holes made along the side for the boat to fire arrows and guns through.

Oarsmen – 10 oars on each side, each were pulled by two men during fair conditions and five in foul seas or combat.

Depending on where you read your history on the Turtle boat, some historians believe there were only two decks but some say three. Yi Soon-Sin may have experimented with both configurations.

There was a crew of 50 marines and up to 70 oarsmen.

Because the Japanese favoured method of combat was to ram the ship and then board, iron cladding was added to the hull.

On the deck a roof was made and covered with planks and spikes. Remembering the Japanese preferred to get close to the boat, board and engage in hand-to-hand combat. The spikes stopped this, as the soldiers were impaled on them!

The Turtle boat was very manoeuvrable and could turn tightly and quickly.

Double agent plot.

Yi was winning battle after battle against the Japanese. He was attacking supply boats that were bringing in food, weapons and troops to the Japanese army.

The Japanese put a spy  (Yosira) in the Joseon Court. The spy was very effective and worked as a double agent, he laid the plan for a trap that would lead to the hoped death of Yi Soon-Sin.

The order came from the King Seonjo, that the Japanese Army would be at the certain point and Yi Soon-Sins Navy was to meet them in battle. Yi Soon-Sin was aware this was a bad area of the coast with lots of rocks below the surface, he was also aware of the spy and refused the order. As a consequence of refusing a direct order by the King, Yi Soon-Sin was arrested and taken in chains to Seoul where he was imprisoned and tortured. He was spared death and eventually released as an inventory soldier. This was the second time for Yi soon-Sin. The Koreans lived by honour, so this was a very severe punishment. The punishment is call Baegui Jonggun

After the Battle of Chilchonryang where Won Gyun (Yi’s successor) took the entire fleet of 150 warships and 30000 men. He was met by a much large Japanese fleet of between 500 -1000 ships. The outcome was devastating with only 12 Korean ships surviving.

When the King heard of the battles result he quickly pardoned Yi and reinstated him.

Battle of Myeongnyang

This battle is a great example of Yi Soon-Sins strategic thinking and the courage he instilled in his men. Korea was outnumbered 25:1.

This battle was a turning point. Yi Soon-Sin now only had 12 ships under his command. None were his favoured Turtle boats.

Japan came with 300 ships, Yi Soon-Sin lured them into the Myeongnyang Strait. This was a treacherous piece of water, the Korean ships could hide against the hill side in deep water. Steel chains were laid in the narrow strait; these went from one side to another and sat below the surface of the water. Once the ships had entered, these chains were tightened and this reduced the moveability of the Japanese boats. Many boats were caught in the fast currents and smashed against the rocks.

The weather was also misty that day, which gave great camouflage for the Korean boats.

Japan lost 31 boats, Korea lost no boats and only 10 casualties.

Yi Soon-Sin had many great battles, he was a great strategist, and always had a plan. He was always out numbered, but had such great loyalty from his men, that they believed they could win and went into battles as the winners. His men trusted and admired him; it was an honour to be lead by him.

An example is during August 1592, 100 000 Japanese troop reinforcements headed around the Pyongyang Peninsula and up the west coast. Admiral Yi Soon-Sin confronted them among the islands off the southern coast of Korea, pre tending at first to flee, he then turned and began to ram the Japanese boats. His fleet copied and eventually 71 Japanese vessels were sunk. When the next wave of vessels arrived he sunk 48 of them. This battle crushed Japans thoughts of invading China.

He then took the entire Korean Navy (180) ships into the Japanese homeport of Pusan and attacked the Japanese naval force of more than 500 ships that were still at anchor. He sank over half of the Japanese ships.

Another example of his strategic thinking was in-between battles there was down time. He had his men make salt by evaporating seawater, this was used to pay local workers for building ships and barracks, and to trade for materials the navy needed. His energy and patriotism was so great that many men worked for free.

China was also helping to fund the Korean war effort. Remembering Japan was coming through Korea on its way to China.

China sent an Admiral Chil Lin, he was not as competent as Yi Soon-Sin. Yi Soon-Sin would offer strategic advise and this would help Admiral Chil Lin win the battles. He was not a proud man, he was happy for this to happen as it kept China feeling positive about supporting the war effort, which supported his beloved country of Korea.

The final battle; Battle of Noryang

Korea had 85 boats ( 82 panokseon and 3 turtle boats) Again out numbered significantly by the Japanese. Yi Sun-sin used the environment to his advantage, the narrow straits and rushing tidal flow.

As the Japanese retreated Yi ordered pursuit. During this time a stray arquebus (gun)bullet from an enemy ship struck General Yi near his left armpit. Sensing it was fatal, he said to his son and nephew

            “the war is at its height – wear my armour and beat my war drums. Do not announce my death”

They then carried him quickly below deck and the nephew put on his armour and continued on with the campaign.

It is said when his death was announced both Korean and Japanese soldiers wailed in grief.


Today, Admiral Yi Soon-Sin is considered one of Korea’s greatest heroes of all time. Koreans look upon Yi Soon-Sin as a man of courage, perseverance, strength, self-sacrifice, intellect, who showed great loyalty to his country.

He was posthumously awarded the title Choong-Moo – meaning loyalty – chivalry.

In 1643 he was awarded the 3rd highest honour the Distinguished Military Service Medal of the Republic of Korea.


“Your Highness, I still have twelve warships”

The King sent orders to close the navy and concentrate on land warfare. Yi wanted to carry on, and the next battle was the Battle of Myeongnyang.

“Those willing to die will live, and those willing to live will die”

Said on the eve of the battle of Myeongnyang, stressing the need to be mentally strong.


International Taekwon Do Techniques Handbook for Colored Belts 2014 edition

Wikipedia – the following sites: Yi Sun-sin , History or Korea, Naval History of Korea, Turtle ship, Immortal Admiral Yi Sun – sin, Battle of Myeongrayang

2nd Dan Essay by Alisdair Hamblyn 2016

Taekwon Do Patterns (Tul) 3rd Edition, revised 2015 Sabum Dale Copeland.

Rosemary Pettit, 3rd Dan

Silla Taekwon-do