The Battle of Sacheon

The Battle of Sacheon was a significant naval conflict during the Japanese invasions of Korea (1592–1598), known as the Imjin War. Fought on June 7, 1592, it marked a decisive victory for the Korean forces led by Admiral Yi Sun-sin, who utilized the innovative turtle ship (Geobukseon) for the first time in combat. The battle demonstrated the effectiveness of Korean naval tactics and the turtle ship’s formidable design, contributing to Admiral Yi’s growing reputation as a brilliant military strategist. This victory disrupted Japanese supply lines and boosted Korean morale during a critical phase of the war.

Sacheon: Yi’s Mighty Turtle Ships

Introduction

In July of 1592, the Japanese commander who stood overlooking the Bay of Sacheon in Korea was probably quite pleased. The invasion of Korea was proceeding as planned; a force of more than 160,000 Japanese samurai had captured Pusan, Korea’s main port, then marched north and seized the capital city of Seoul. The great Japanese warlord Toyotomi Hideyoshi, the mastermind behind the invasion, was well on his way to extending his dominion to include Korea and, using that foothold, to conquer China. The only blotch on the invasion’s record of triumphs occurred when an unusually aggressive Korean admiral, Yi Sun-shin, caught and destroyed several dozen Japanese vessels. Now, this same Yi Sun-shin has been sighted sailing into Sacheon Bay.

The Battle of Sacheon

• (1) On July 8, 1592, the Korean admiral Yi Sun-shin had been sighted sailing into Sacheon Bay at the head of his squadron, and the commander of the Japanese invasion at once ordered his men to attack. Confirming the Japanese opinion of the unwarlike nature of the Koreans, as soon as the Japanese warships began pouring out into the bay, the Koreans retreated.
• (2) The Japanese eagerly pursued, and the Korean craft suddenly turned smartly about and headed back toward the Japanese. The apparent fight had been a ruse to lure the Japanese out into open water. No matter; the Japanese were confident of success and moved to engage the Koreans.
• (3) Then a terrifying sight emerged: A dragon’s head spitting smoke and a flame connected to a strange, bulky, low-lying body. There was no open deck, and no humans were visible; instead, the creature had a curved, humped back formed from interlocking hexagonal plates with sharp, tapering spines. From small holes along its sides, cannons discharged deadly hail. This monster plunged into the midst of the Japanese ships, spewing death and destruction.
• (4) While the creature wreaked havoc and confusion among the Japanese, the rest of the Korean fleet, more conventionally designed vessels, stood at a distance and bombarded the Japanese with cannons and arrows.
• (5) The Battle of Sacheon turned into a slaughter, with the confused Japanese trapped between the guns of the impregnable monster and the storm of missiles from the Korean ships that surrounded them.
• (6) The battle marked the combat debut of the turtle ship. Over the next decade, Yi and his turtle ships would play a key role in defeating Japan’s invasions of Korea, and Yi’s actions would establish him as one of the greatest admirals of all time.

The Opponents

• (1) Yi Sun-shin was born in 1545 and decided to pursue a military career. According to a story that may be apocryphal, the first time Yi attempted to pass the rigorous military entrance examinations, he fell off his horse, breaking his leg. Though he knew he had failed the exam, he splinted the break using the branch of a nearby tree and completed the exercise. After passing the exam in a later year, he rose through the ranks, distinguishing himself in action.
• (2) Advancement in the Korean political and military structure was heavily based on favoritism and patronage rather than ability, and thanks to the support of a childhood friend who had influence at court, Yi was the commander of a small contingent of the Korean fleet when the Japanese attacked in 1592.
• (3) Yi kept a diary that has mostly survived and is available in English translation. in addition to its historical importance for the first-hand descriptions it gives of major battles and key events surrounding the invasion of Korea, it also offers a unique and humanizing portrait of a legendary figure.
• (4) At the Battle of Sacheon, one of the very few casualties was suffered by Admiral Yi, who was shot in the shoulder by a Japanese musket. This incident also proved prophetic, in that Yi would suffer several more combat injuries, culminating in his death in battle.
• (5) The driving force behind the invasion was the Japanese warlord Toyotomi Hideyoshi. He joined the army of one of Japan’s lords as a common foot soldier, repeatedly distinguished himself in battle, and rose to the level of general.
• (6) Some opportune deaths combined with his own talent and ambition allowed Hideyoshi to become one of the major powers in Japan, and he solidified his reputation with a bold invasion of the southern island of Japan, Kyoshu. The conquest of Kyoshu had involved a large-scale amphibious landing, and this may have given Hideyoshi the idea for the invasion of Korea.
• (7) Kyoshu is separated from the Korean mainland by only 30 miles of water, known as the Tsushima Straits. Several islands in the Straits provide useful waypoints and visual guidance. It is an easy crossing—not only an important trade route but an invasion path both to and from Japan.

Japanese Naval Warfare

• (1) For the Japanese, battles at sea were simply extensions of land combat, and they attempted to use similar tactics. Thus, Japanese warships were designed less as weapons in their own right than as platforms for infantry, and the main tactic in naval battles was to run one ship up alongside another and let the two crews fight it out hand-to-hand. Primitive cannons were in use but were rarely placed on ships, and the firepower of a Japanese warship came entirely from the personal weapons carried by her crew.
• (2) The samurai had a long tradition of excellence at archery, and every samurai would have been trained in the use of the Japanese longbow. Recently, however, gunpowder had arrived on Japanese battlefields, and a major component of armies was now foot soldiers armed with an early form of musket.
• (3) The largest and most specialized type of Japanese warship, the ataka bune, had high, flat, wooden sides pierced at regular intervals with loopholes through which the men within could fire their guns. A line of oars projected from a lower row of holes, and there was usually one mast with a square sail, typically lowered during battle. On the flat roof of the main cabin, more infantry were stationed, and sometimes there was a tower. The crew consisted of around 80 oarsmen and 60 fighting men. As a ship, it was slow, ponderous, and not very seaworthy.
• (4) Next in size was the seki bune, basically a smaller version of the ataka bune. It had a tapered bow and was either partially enclosed or had a waist-high railing protecting the crew. Somewhat more maneuverable, it carried around 40 oarsmen and 30 soldiers.
• (5) The smallest, swiftest craft was the kobaya, which had an open deck and was really just a small ship carrying some soldiers. To offer some token protection, the Japanese often built a wooden framework from which they hung fabric screens. These might offer enough resistance to catch an arrow that was nearly spent, but would not have stopped a more forceful projectile.

Korean Naval Warfare

• (1) The Koreans approached naval combat with a different strategy. Rather than closing with the enemy and boarding, they preferred to stand off at a distance and bombard an enemy vessel with cannonballs, firebombs, bullets, and arrows.
• (2) The standard Korean warship, the panokson, was medium-sized and had two decks: an enclosed lower one that protected the rowers and a wide upper fighting deck surrounded by railings. The larger models might also have a tower on the upper deck. They were solidly constructed to bear the weight of cannons.
• (3) Each panokson had a variety of cannons of different sizes and ranges. All fired stone and iron cannonballs, as well as incendiary bombs. The Koreans also used them to propel enormous wooden arrows equipped with iron tips and leather vanes, said to cause massive destruction when they struck their target.
• (4) Admiral Yi’s famed turtle ships were propelled by the usual mixture of oars and a
  mast carrying a square sail, but because of their shape, they were especially maneuverable. They mounted about six cannons on each side, with several more firing to the front and back.
• (5) Because of its especially sturdy design and thick protection, the turtle ship was capable of ramming its opponents, but the preferred method of combat was to sink enemy vessels with shots from its cannons or to set them afire.

The Battle of Hansan Island

• (1) Recognizing the danger Yi posed, Hideyoshi ordered his generals to destroy Yi and his ships, leading to Yi’s greatest victory, the Battle of Hansan Island.
• (2) Yi again used a false retreat by to lure the Japanese into a stretch of open water near Hansan Island. The Japanese raced after the Korean ships and found themselves confronting the main Korean fleet in a crescent-shaped formation. The Japanese were drawn toward the center of this formation, where Yi encircled them.
• (3) At the center of the Korean formation were the turtle ships, and Yi now ordered these to move forward to engage and hold the Japanese, while the panokson circled around them and began their bombardment. Once again, the Japanese were slaughtered, and the entire fleet was wiped out.

Outcomes

• (1) Korea was weakened and devastated by the Japanese invasion, but the spirited defense offered by the Koreans eventually became the foundation of nationalism and independence.
• (2) In Japan, the thwarted invasions marked the country’s first attempt to acquire an empire on the mainland of Asia—a dark ambition revived with global effects in the 20th century.

Conclusion

The Battle of Sacheon concluded with a decisive victory for the Korean navy under Admiral Yi Sun-sin. The effective use of the turtle ship (Geobukseon) demonstrated the superiority of Korean naval tactics and technology, inflicting heavy losses on the Japanese fleet and preventing them from securing a crucial foothold in Korean waters. This victory not only disrupted the Japanese supply lines but also bolstered Korean morale at a critical juncture in the Imjin War. The success at Sacheon solidified Admiral Yi’s reputation as a brilliant strategist and played a significant role in the continued resistance against the Japanese invasion, contributing to the eventual failure of Japan’s campaign in Korea.

(FAQ) about the Battle of Sacheon