[10] According to Chungmugonghaengjang (충무공행장; 忠武公行狀), a biography believed to have been published during King Sunjo's reign, Yi moved to Asan before the age of eight,[8] where his future wife's family resided.

Yi's efforts in northern Korea were rewarded when he was assigned as Commander of the Jeolla Province (전라 좌도; 全羅左道) Left Naval District.

[note 1] The royal court was in a state of confusion over the possibility of a war with Japan, now unified under the rule of Toyotomi Hideyoshi, and the unstable situation in Manchuria where a young Jurchen chieftain named Nurhaci was gathering strength.

They reached Seoul in just nineteen days, on May 2, 1592, due to the military inefficiency of the Joseon army, especially at the Battle of Sangju and the failure to defend Joryeong Pass.

After capturing Hanseong and Pyongyang, the Japanese planned to cross the Yalu River into Chinese territory, and use the waters west of the Korean peninsula to supply the invasion.

In response to the Korean navy's success, Toyotomi Hideyoshi recalled three admirals from land-based activities: Wakizaka Yasuharu, Kato Yoshiaki, and Kuki Yoshitaka.

[18] With at least three turtle ships (two of which were newly completed) spearheading the clash, the Korean vessels fired volleys of cannonballs into the Japanese formation.

Some historians maintain that, since Yi was a unique individual and often pursued innovative ideas (contrary to the established wisdom of his peers), it is possible that he had the turtle ship built with three decks.

[citation needed] Yi would stay under General Gwon Yul's command for a short while until Won Gyun's death at the Battle of Chilchonryang, which would lead to his reinstatement.

Without adequate reconnaissance or planning, Won Gyun decided to attack with the entire naval force of Joseon at his disposal; a fleet consisting of 150 warships operated by 30,000 men that had been carefully assembled and trained by Admiral Yi.

When King Seonjo and the royal court learned of the catastrophic defeat, they hurriedly pardoned and reinstated Admiral Yi as commander of the greatly reduced Joseon fleet.

In the belief that the Joseon fleet would never be restorable, King Seonjo, sent an edict to Admiral Yi to abandon the warships and take his men to join the ground forces under General Gwon Yul.

The unpredictable current eventually wreaked havoc on the Japanese; their ships found themselves unable to maneuver and collided with each other when the tide reversed, while also presenting a perfect target for the Joseon naval artillery.

Kurushima Michifusa was killed on his flagship by Joseon archers; his body in its ornate armor was fished out of the water and his severed head was put on display to further demoralize the Japanese fleet.

On December 15, 1598, a huge Japanese fleet under the command of Shimazu Yoshihiro, was amassed in Sachon Bay, on the east end of Noryang Strait.

Shimazu's goal was to break the allied forces' blockade on Konishi Yukinaga, join the two fleets, and sail home to Japan.

The tightness of Noryang Strait hindered lateral movement, and Yi's maneuvers prevented the Japanese fleet from boarding their enemies' vessels, their primary naval tactic.

[35] News of Admiral Yi's death spread quickly throughout the allied fleet and both Joseon and Ming sailors and fighting men wailed in grief.

[37][38] According to Ballard: It is always difficult for Englishmen to admit that Nelson ever had an equal in his profession, but if any man is entitled to be so regarded, it should be this great naval commander of Asiatic race who never knew defeat and died in the presence of the enemy; of whose movements a track-chart might be compiled from the wrecks of hundreds of Japanese ships lying with their valiant crews at the bottom of the sea, off the coasts of the Korean peninsula... and it seems, in truth, no exaggeration to assert that from first to last he never made a mistake, for his work was so complete under each variety of circumstances as to defy criticism... His whole career might be summarized by saying that, although he had no lessons from history to serve as a guide, he waged war on the sea as it should be waged if it is to produce definite results, and ended by making the supreme sacrifice of a defender of his country.

Napoleon, who mastered the art of conquering the part with the whole, can be held to have been such a general, and among admirals, two further tactical geniuses may be named: in the East, Yi Sun-sin of Korea, and in the West, Horatio Nelson of England.

Undoubtedly, Yi is a supreme naval commander even on the basis of the limited literature of the Seven-Year War, and despite the fact that his bravery and brilliance are not known to the West, since he had the misfortune to be born in Joseon period.

– A Military History of the Empire (Japanese: 帝國國防史論), p. 399Although the Korean royal court often ignored his successes during his life, after his death various honors were bestowed upon him, including the title of Chungmugong (충무공; 忠武公; Duke of Loyalty and Warfare), an enrollment as a Seonmu Ildeung Gongsin (선무일등공신; 宣武一等功臣; First-class military order of merit during the reign of Seonjo), and two posthumous offices, Yeonguijeong (영의정; 領議政; Prime Minister), and the Deokpung Buwongun (덕풍부원군; 德豊府院君; The Prince of the Court from Deokpung).

In North Korea, the military awards the Order of Admiral Yi Sun-Sin (이순신장군훈장) to flag officers and naval commanders for outstanding leadership.

Admiral Yi repeatedly defeated the Japanese invasion force in battle, while preserving the lives of his soldiers and respecting their families.

The conspiracies worked against Admiral Yi from gaining the men, materiel, and operational freedom to decisively destroy the Japanese invasion force.

The city of Chungmu on the southern coast of Korea, now renamed Tongyeong, is named in honor of his posthumous title and the site of his headquarters.

Unusually, the film presented Yi as a cunning, slightly eccentric young man, rather than a distinguished austere hero, a couple of decades before Imjin war.

The film's theme clearly uses the figure of Yi, venerated as a hero in both parts of present-day Korea, to plead for Korean reunification.

The drama was criticized for the many artistic licenses taken, such as depicting Yi as weak and lonely in his early life and taking liberties with the events surrounding his death.

This drama was a heated topic at the time since it overlapped with rising tensions in the ongoing Liancourt Rocks dispute; the series further strained relations between South Korea and Japan in the issue's most recent outbreak.