King Sejong the Great of Korea

Statue of King Sejong in Seoul

Starcevic/Getty ImagesĀ 

Korea's sage-king, Sejong the Great, was troubled. His country was a tributary state of Ming China, and used Chinese characters to write the Korean language. However, this presented several problems for the people of Joseon Korea:

The sounds of our language differ from those of Chinese and are not easily communicated by using Chinese graphs. Many among the ignorant, therefore, though they wish to express their sentiments in writing, have been unable to communicate. Considering this situation with compassion, I have newly devised twenty-eight letters. I wish only that the people will learn them easily and use them conveniently in their daily life.

This statement by King Sejong (r. 1418 - 1450) demonstrates that literacy and education were already important values in Korean society six hundred years ago. It also shows the king's concern for the common people - an amazingly democratic approach for a ruler in the middle ages.

Birth and Succession

Sejong was born under the name Yi Do to King Taejong and Queen Wongyeong of Joseon on May 7, 1397. The third of the royal couple's four sons, Sejong impressed all of his family with his wisdom and curiosity.

According to Confucian principles the eldest son, Prince Yangnyeong should have been the heir to the Joseon throne. However, his behavior at court was rude and aberrant. Some sources claim that Yangnyeong behaved this way purposefully because he believed that Sejong should be king in his place. The second brother, Prince Hyoryeong, also removed himself from the succession by becoming a Buddhist monk.

When Sejong was 12 years old, his father named him "Grand Prince Chungnyeong." Ten years later, King Taejong would abdicate the throne in favor of Prince Chungnyeong, who took the throne name King Sejong.

Background - The Strife of Princes

Sejong's accession to the throne was unusually easy and bloodless. How many times in history have two elder brothers simply bowed out of the competition for a crown, after all? It may well be that the Joseon dynasty's short but sordid history played an important role in this outcome.

Sejong's grandfather, King Taejo, overthrew the Goryeo Kingdom in 1392 and founded Joseon. He was assisted in the coup d'etat by his fifth son, Yi Bang-won (later King Taejong), who expected to be rewarded with the title of Crown Prince. However, a court scholar who hated and feared the militaristic and hot-headed fifth son convinced King Taejo to name his eighth son, Yi Bang-seok, as successor instead.

In 1398, while King Taejo was mourning the loss of his wife, the scholar hatched a conspiracy to kill off all of the king's sons besides the Crown Prince, in order to secure Yi Bang-seok's position (and his own). Hearing rumors of the plot, Yi Bang-won raised his army and attacked the capital, killing two of his brothers as well as the scheming scholar.

The grieving King Taejo was horrified that his sons were turning on each other in what became known as the First Strife of Princes, so he named his second son, Yi Bang-gwa, as the heir apparent, and then abdicated the throne in 1398. Yi Bang-gwa became King Jeongjong, the second Joseon ruler.

In 1400, the Second Strife of Princes broke out when Yi Bang-won and his brother, Yi Bang-gan, began to fight. Yi Bang-won prevailed, exiled his brother and family, and executed his brother's supporters. As a result, the weak King Jeongjong abdicated after ruling for just two years in favor of his brother, Yi Bang-won. Yi Bang-won became King Taejong, the third Joseon ruler, and Sejong's father.

As king, Taejong continued his ruthless policies. He executed a number of his own supporters if they became too powerful, including all of his wife Wong-gyeong's brothers, as well as Prince Chungnyeong's (later King Sejong's) father-in-law and brothers-in-law.

It seems likely that his experience with princely strife, and his willingness to execute troublesome family members, helped encourage his first two sons to step aside without a murmur and allow King Taejong's third and favorite son to become King Sejong.

Sejong's Military Developments

King Taejong had always been an effective military strategist and leader, and he continued to guide Joseon military planning for the first four years of Sejong's reign. Sejong was a quick study, and also loved science and technology, so he introduced a number of organizational and technological improvements to his kingdom's military forces.

Although gunpowder had been used for centuries in Korea, its employment in advanced weaponry expanded markedly under Sejong. He supported the development of new types of cannons and mortars, as well as rocket-like "fire arrows" that functioned in a similar way to modern RPGs (rocket-propelled grenades).

Gihae Eastern Expedition

In May of 1419, just one year into his reign, King Sejong dispatched the Gihae Eastern Expedition to the seas off Korea's east coast. This military force set out to confront the Japanese pirates or wako who operated out of Tsushima Island, harrying shipping, stealing trade goods, and kidnapping Korean and Chinese subjects.

By September of that year, the Korean troops had defeated the pirates, killing nearly 150 of them, and rescuing almost 150 Chinese kidnap victims and 8 Koreans. This expedition would bear important fruit later in Sejong's reign, as well. In 1443, the daimyo of Tsushima pledged obedience to the King of Joseon Korea in the Treaty of Gyehae, in exchange for which he received preferential trading rights with the Korean mainland.

Sejong's Family

King Sejong's queen was Soheon of the Shim clan, with whom he eventually would have a total of eight sons and two daughters. He also had three Royal Noble Consorts, Consort Hye, Consort Yeong, and Consort Shin, who bore him three sons, one son and six sons, respectively. In addition, Sejong had seven lesser consorts who had the misfortune of never producing sons.

Nevertheless, the presence of eighteen princes representing different clans on their mothers' sides ensured that in the future, the succession would be contentious. As a Confucian scholar, though, King Sejong followed protocol and named his sickly eldest son Munjong as Crown Prince.

Sejong's Achievements in Science, Literature, and Policy

King Sejong delighted in science and technology, and supported a number of inventions or refinements of previous technologies. For example, he encouraged the improvement of a moveable metal type for printing first used in Korea by 1234, at least 215 years before Gutenberg, as well as the development of the sturdier mulberry-fiber paper. These measures made better-quality books much more widely available among educated Koreans. Among the books, Sejong sponsored were a history of the Goryeo Kingdom, a compilation of filial deeds (model actions for followers of Confucius to emulate), and farming guides meant to help farmers improve production.

Other scientific devices sponsored by King Sejong included the first rain gauge, sundials, unusually accurate water clocks, and maps of the stars and celestial globes. He also took an interest in music, devising an elegant notation system for representing Korean and Chinese music, and encouraging instrument-makers to improve the designs of various musical instruments.

In 1420, King Sejong established an academy of twenty top Confucian scholars to advise him, called the Hall of Worthies. The scholars studied the ancient laws and rites of China and previous Korean dynasties, compiled historical texts, and lectured the king and crown prince on Confucian classics.

In addition, Sejong ordered one top scholar to comb the country for intellectually talented young men, who would be given a stipend to retreat for one year from their work. The young scholars were sent to a mountain temple where they were allowed to read books on a vast array of subjects including astronomy, medicine, geography, history, the art of war, and religion. Many of the Worthies objected to this expansive menu of options, believing that a study of Confucian thought was sufficient, but Sejong preferred to have a scholar class with a wide range of knowledge.

To aid the common people, Sejong established a grain surplus of approximately 5 million bushels of rice. In times of drought or flood, this grain was available to feed and support poor farming families, preventing famine.

Invention of Hangul, the Korean Script

The one invention that King Sejong is most remembered for today, however, is that of hangul, the Korean alphabet. In 1443, Sejong and eight advisers developed an alphabetic system to represent Korean language sounds and sentence structure accurately. They came up with a simple system of 14 consonants and 10 vowels, which can be arranged in clusters to create all of the sounds in spoken Korean.

King Sejong announced the creation of this alphabet in 1446 and encouraged all of his subjects to learn and use it. Initially, he faced a backlash from the scholar elite, who felt that the new system was vulgar (and who probably did not want women and peasants to be literate). However, hangul quickly spread among segments of the population who previously had not had access to enough education to learn the complicated Chinese writing system.

Early texts claim that a clever person can learn Hangul in a few hours, while a stupid person can master it in 10 days. Certainly, it is one of the most logical and straight-forward writing systems on Earth - a true gift from King Sejong to his subjects and their descendants, down to the present day.

King Sejong's Death

King Sejong's health began to decline even as his accomplishments mounted. Suffering from diabetes and other health problems, Sejong became blind around the age of 50. He passed away on May 18, 1450, at the age of just 53.

As he had predicted, his eldest son and successor Munjong did not survive him by long. After just two years on the throne, Munjong died in May of 1452, leaving his 12-year-old first son Danjong to rule. Two scholar-officials served as regents for the child.

This first Joseon experiment in Confucian-style primogeniture did not last long, however. In 1453, Danjong's uncle, King Sejong's second son Sejo, had the two regents murdered and seized power. Two years later, Sejo formally forced Danjong to abdicate and claimed the throne for himself. Six court officials formed a plan to restore Danjong to power in 1456; Sejo discovered the scheme, executed the officials, and ordered his 16-year-old nephew burned to death so that he could not serve as a figurehead for future challenges to Sejo's title.

Sejong the Great's Legacy

Despite the dynastic mess that resulted from King Sejong's death, he is remembered as the wisest and most capable ruler in Korean history. His accomplishments in science, political theory, military arts and literature mark Sejong as one of the most innovative kings in Asia or the world. As shown by his sponsorship of Hangul and his establishment of the food reserve, King Sejong truly cared about his subjects.

Today, the king is remembered as Sejong the Great, one of only two Korean kings honored with that appellation. The other is Gwanggaeto the Great of Goguryeo, r. 391 - 413. Sejong's face appears on the largest denomination of South Korea's currency, the 10,000 won bill. His military legacy also lives on in the King Sejong the Great class of guided missile destroyers, first launched by the South Korean navy in 2007. In addition, the king is the subject of a Korean television drama series, Daewang Sejong or "King Sejong the Great," starring Kim Sang-kyung in the title role.


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Kim, Chun-gil. The History of Korea, Westport, CT: Greenwood Publishing, 2005.

"King Sejong the Great and the Golden Age of Korea," Asia Society, accessed Nov. 25, 2011.

Lee, Peter H. & William De Bary. Sources of Korean Tradition: From Early Times through the Sixteenth Century, New York: Columbia University Press, 2000.