Oei Invasion

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  • Dates: 1419/6/20-9/29

The Ôei Invasion was an attack on the island of Tsushima launched in 1419 by Joseon Dynasty Korea.

Though controlled by the Sô clan for centuries, Tsushima (K: Daemado) was believed by the Joseon court to have been Korean territory in ancient times, and to be wrongfully occupied by the Japanese. Further, in the 14th-15th centuries, the island had become a major center of wakô ("pirate") activity. One wakô leader, Sôda Saemontarô, traveled throughout the region acting as an official agent of the Sô clan samurai lord of Tsushima; according to some scholars, the perceived threat of Sôda in particular was a notable factor contributing to the Korean decision to attack Tsushima at this time.[1]

On 1419/6/9, Taejong, former King of Korea, and/or his successor King Sejong, declared war on Tsushima. Ten days later, on 6/19, a fleet of Korean warships set sail for Tsushima under the command of Yi Jong-mu. The fleet, consisting of some 17,000 men on 227 ships, arrived at the island the following day.

Japanese forces performed a successful ambush against their Korean counterparts on 6/26, in what is known as the Battle of Nukadake. A cease-fire was called on 7/3, and the Korean fleet withdrew for a time. However, fighting eventually resumed, and ended in the head of the Sô clan surrendering to the Korean forces on 9/29.

Gallery labels at the "Story of King Sejong" museum in Seoul represent these events as the successful "subjugation" of Daemado; however, the invasion did not result in any notable political changes. The samurai Sô clan remained in control of the island, and remained subordinate or deferential to the Joseon court, as they already had been in the past. Though the Sô regularly dispatched envoys to pay respects and tributary gifts to the Joseon court, and otherwise acted the role of a Korean vassal well into the 19th century, the island never came under Korean control and remains part of Japan today. Despite the Sô formally surrendering to Korean forces, many in Japan at the time considered the invasion to have been stopped, defeated, by Hachiman, one of the chief deities credited with stopping the Mongol invasions roughly a century and a half earlier; though by 1419 both the Mongol Empire (Yuan dynasty in China) and the closely-affiliated Goryeo dynasty in Korea had fallen, and the attackers thus had no connection with the Mongols, most in Japan at the time were not aware of these details and drew strong associative connections between the events.[2]

In the 1440s, Joseon and the Sô reached an agreement to help curb the pirate problem; the Sô would take on the responsibility of cracking down on smuggling and pirate activity, and enforcing a system of trading licenses, in exchange for stipends and trading rights for themselves.[3]


  • Gallery labels, Story of King Sejong Museum, Seoul.[1]
  1. Gregory Smits, Maritime Ryukyu, University of Hawaii Press (2019), 42.
  2. Smits, Maritime Ryukyu, 44.
  3. Robert Hellyer, Defining Engagement, Harvard University Press (2009), 31.