Yi Sun-sin: history’s greatest admiral

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Yi Sun-sin
Yi Sun-sin. Image: Alamy

When we think of great naval commanders, we immediately think of Horatio Nelson. He fought 13 battles, winning eight.

Admiral Yi Sun-sin (1545-1598) fought 23 battles against the Japanese invaders of Korea between 1592 and 1598, and won every one of them without losing a single ship. In 14 of these battles, moreover, not a single Japanese ship survived.

Yet Yi Sun-sin was an amateur: he had no formal naval training of any kind.

Japan’s greatest admiral, Heihachiro Togo, the victor of Tsushima, said: ‘It may be proper to compare me to Nelson, but not to Korea’s Yi Sun-sin. He is too great to be compared to anyone.’

While conducting his campaigns, Admiral Yi got virtually no support from his colleagues or the Korean court. Even worse, he was demoted to the ranks more than once on trumped-up charges due to the intrigues of jealous rivals.

How was he able to accomplish so much, and why was Japan unable to defeat him, even though it won nearly every land battle fought at the same time?


Use of the term ‘military revolution’ to describe developments in warfare between 1500 and 1800 has been in question for many years. Yet however we describe it – and perhaps ‘revolution’ is too strong a term for such a protracted, evolutionary process – the advent of gunpowder, the growing size and professionalism of armed forces, the increasing application of science to the military art, notably in fortification and sieges, these and other changes represented radical transformation.

The men who fought at Hastings in 1066 would have understood the battlefield of Bosworth in 1485. They would have been mightily impressed by the quality of the armour, and no doubt disconcerted by the firepower of bombards and hand-guns, but they would have been familiar with the scale and tactics of the battle.

But place the men of Bosworth on the battlefield of Waterloo (1815), Blenheim (1704), or even Naseby (1645), and they would have been confounded.

Between 1500 and 1800, armies of thousands had become armies of tens of thousands, ‘bill and bow’ and given way to ‘horse and musket’, the feudal retinue had been replaced by highly drilled battalions of professionals, and living off the land had given way to complex logistical chains.

The transformation at sea was no less complete. Medieval naval battles had taken the form of land battles, fleets packed with cohorts of heavily armed men bumping into contact and then slugging it out on the gangplanks and upper decks. Even the ram – whose successful use required subtle manoeuvre – was in abeyance in the medieval period.

But as early as the late 16th century, cannon had acquired such power that it became possible to blast enemy ships from a distance until they sank or struck their colours.

The distances were still short. Even in Nelson’s time, broadsides had to be delivered at thousand yards or less to be effective, and the closer the better. But what a difference this was. Ships were now floating gun-platforms, not troop-carriers.

All this is very familiar to English-speaking military historians. Much more obscure – because of the language barrier between Western and Eastern scholars – is the ‘military revolution’ under way on the opposite shores of Eurasia, where Japanese, Chinese, and Korean warfare was also being transformed by gunpowder.


Painting showing the building of the 'Turtle Ship'.
Building the ‘Turtle Ship’. Image: Alamy

Korea’s secret weapon was the kobukson (‘turtle ship’), invented in 1413. When King Taejong (1401-1418) saw them fighting Japanese pirates in 1415, he realised their potential: ‘While turtle ships can infiltrate and attack enemy vessels, the enemy cannot effect harm on the assaulting ships.’

The Japanese called them ‘blind ships’, because they fought as fearlessly as a blind warrior. There were never more than six in use at one time.

After more than 150 years of peace, they had fallen out of use. Fortunately, the building method was still known to the great shipbuilder Na Tae-yong. Under Yi, he began constructing a fleet of them with little time to spare. The first new turtle ship was finished on 12 April 1592. The very next day, the Japanese invasion began.

Turtle ships were 34.2m long, 10.3m wide, and 6.4m high. They were armed with up to 26 cannon, with six gun ports on each side. At the prow was a dragon’s head. Through its mouth could be fired cannonballs, flames, or sulphur smoke-clouds.

The Koreans had been using cannon against Japanese pirates since 1380. They came in four sizes: heaven, earth, black, and yellow. To prevent boarding, the ships had a roof of iron spikes hidden by straw mats.

The Koreans could see out, but the Japanese could not see in. There were two decks. On the lower deck were 80 oarsmen, with eight oars on either side, each with a leader and four rowers. Usually oars and sails were used in combination, but in battle the sails were lowered. On the upper deck were 45 archers and gunners.

The failure of the Japanese navy against the turtle ship resembles the defeat of the Spanish Armada by English warships in 1588. Like Spanish galleons, the Japanese ships were used as floating castles, holding as many soldiers as possible for amphibious warfare. Their preferred method of combat was grappling and boarding enemy ships.

Both Japanese and Spanish ships were top-heavy, which limited their manoeuvrability and firepower. Japan’s ships could carry only two or three cannon each, as the recoil from more would have capsized them.

By contrast, the Korean and English ships were designed for naval instead of amphibious warfare. Their purpose was the destruction of enemy ships with concentrated firepower. Their sleeker design meant they could carry more cannon.

Thus, Yi used innovative tactics and superior ships to tear the heart out of the Japanese fleets he encountered, and destroyed any chance they might have had of supplying their forces in the north of Korea.

Within a matter of weeks, Yi engineered one of the most startling reversals of fortune in all military history. Lacking supplies and reinforcements, there was no way Japanese commander Hideyoshi could maintain his offensive and go on to invade China.

Ming Chinese soldiers intervened against the invaders, too. The Japanese were forced to halt their advance in 1593, retreating back down the peninsula to forts along the southern coast. Korea had been saved.

Edmund West

This is an extract from a 17-page special feature on the Golden Age of the Korean Navy, published in the May 2019 issue of Military History Matters.

To read the full analysis, get a copy of the issue from your local Barnes & Noble or W H Smith, or click here to subscribe to the magazine and have it sent straight to your door every month.

1 Comment

  1. It is true the turtle ship aided in defeating the Japanese invasion but after Yi was prisoned on trump up charges, one of his rival, and instigator of the trumped up charges, Won Kun lost all of their ships including all of turtle ships to 2nd invasion. Only then king realized his mistake and let Yi assume commands with only 13 ships left in his arsenal. Yi managed to defeat 150 Japanese warships plus 150 more support ships with only 13 ships. His genius and courage is unmatched in history of naval battles.

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